// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *  SR-IPv6 implementation
 *
 *  Authors:
 *  David Lebrun <david.lebrun@uclouvain.be>
 *  eBPF support: Mathieu Xhonneux <m.xhonneux@gmail.com>
 */

#include <linux/filter.h>
#include <linux/types.h>
#include <linux/skbuff.h>
#include <linux/net.h>
#include <linux/module.h>
#include <net/ip.h>
#include <net/lwtunnel.h>
#include <net/netevent.h>
#include <net/netns/generic.h>
#include <net/ip6_fib.h>
#include <net/route.h>
#include <net/seg6.h>
#include <linux/seg6.h>
#include <linux/seg6_local.h>
#include <net/addrconf.h>
#include <net/ip6_route.h>
#include <net/dst_cache.h>
#include <net/ip_tunnels.h>
#ifdef CONFIG_IPV6_SEG6_HMAC
#include <net/seg6_hmac.h>
#endif
#include <net/seg6_local.h>
#include <linux/etherdevice.h>
#include <linux/bpf.h>
#include <linux/netfilter.h>

#define SEG6_F_ATTR(i)          BIT(i)

struct seg6_local_lwt;

/* callbacks used for customizing the creation and destruction of a behavior */
struct seg6_local_lwtunnel_ops {
        int (*build_state)(struct seg6_local_lwt *slwt, const void *cfg,
                           struct netlink_ext_ack *extack);
        void (*destroy_state)(struct seg6_local_lwt *slwt);
};

struct seg6_action_desc {
        int action;
        unsigned long attrs;

        /* The optattrs field is used for specifying all the optional
         * attributes supported by a specific behavior.
         * It means that if one of these attributes is not provided in the
         * netlink message during the behavior creation, no errors will be
         * returned to the userspace.
         *
         * Each attribute can be only of two types (mutually exclusive):
         * 1) required or 2) optional.
         * Every user MUST obey to this rule! If you set an attribute as
         * required the same attribute CANNOT be set as optional and vice
         * versa.
         */
        unsigned long optattrs;

        int (*input)(struct sk_buff *skb, struct seg6_local_lwt *slwt);
        int static_headroom;

        struct seg6_local_lwtunnel_ops slwt_ops;
};

struct bpf_lwt_prog {
        struct bpf_prog *prog;
        char *name;
};

/* default length values (expressed in bits) for both Locator-Block and
 * Locator-Node Function.
 *
 * Both SEG6_LOCAL_LCBLOCK_DBITS and SEG6_LOCAL_LCNODE_FN_DBITS *must* be:
 *    i) greater than 0;
 *   ii) evenly divisible by 8. In other terms, the lengths of the
 *       Locator-Block and Locator-Node Function must be byte-aligned (we can
 *       relax this constraint in the future if really needed).
 *
 * Moreover, a third condition must hold:
 *  iii) SEG6_LOCAL_LCBLOCK_DBITS + SEG6_LOCAL_LCNODE_FN_DBITS <= 128.
 *
 * The correctness of SEG6_LOCAL_LCBLOCK_DBITS and SEG6_LOCAL_LCNODE_FN_DBITS
 * values are checked during the kernel compilation. If the compilation stops,
 * check the value of these parameters to see if they meet conditions (i), (ii)
 * and (iii).
 */
#define SEG6_LOCAL_LCBLOCK_DBITS        32
#define SEG6_LOCAL_LCNODE_FN_DBITS      16

/* The following next_csid_chk_{cntr,lcblock,lcblock_fn}_bits macros can be
 * used directly to check whether the lengths (in bits) of Locator-Block and
 * Locator-Node Function are valid according to (i), (ii), (iii).
 */
#define next_csid_chk_cntr_bits(blen, flen)             \
        ((blen) + (flen) > 128)

#define next_csid_chk_lcblock_bits(blen)                \
({                                                      \
        typeof(blen) __tmp = blen;                      \
        (!__tmp || __tmp > 120 || (__tmp & 0x07));      \
})

#define next_csid_chk_lcnode_fn_bits(flen)              \
        next_csid_chk_lcblock_bits(flen)

/* flag indicating that flavors are set up for a given End* behavior */
#define SEG6_F_LOCAL_FLAVORS            SEG6_F_ATTR(SEG6_LOCAL_FLAVORS)

#define SEG6_F_LOCAL_FLV_OP(flvname)    BIT(SEG6_LOCAL_FLV_OP_##flvname)
#define SEG6_F_LOCAL_FLV_NEXT_CSID      SEG6_F_LOCAL_FLV_OP(NEXT_CSID)
#define SEG6_F_LOCAL_FLV_PSP            SEG6_F_LOCAL_FLV_OP(PSP)

/* Supported RFC8986 Flavor operations are reported in this bitmask */
#define SEG6_LOCAL_FLV8986_SUPP_OPS     SEG6_F_LOCAL_FLV_PSP

#define SEG6_LOCAL_END_FLV_SUPP_OPS     (SEG6_F_LOCAL_FLV_NEXT_CSID | \
                                         SEG6_LOCAL_FLV8986_SUPP_OPS)
#define SEG6_LOCAL_END_X_FLV_SUPP_OPS   SEG6_F_LOCAL_FLV_NEXT_CSID

struct seg6_flavors_info {
        /* Flavor operations */
        __u32 flv_ops;

        /* Locator-Block length, expressed in bits */
        __u8 lcblock_bits;
        /* Locator-Node Function length, expressed in bits*/
        __u8 lcnode_func_bits;
};

enum seg6_end_dt_mode {
        DT_INVALID_MODE = -EINVAL,
        DT_LEGACY_MODE  = 0,
        DT_VRF_MODE     = 1,
};

struct seg6_end_dt_info {
        enum seg6_end_dt_mode mode;

        struct net *net;
        /* VRF device associated to the routing table used by the SRv6
         * End.DT4/DT6 behavior for routing IPv4/IPv6 packets.
         */
        int vrf_ifindex;
        int vrf_table;

        /* tunneled packet family (IPv4 or IPv6).
         * Protocol and header length are inferred from family.
         */
        u16 family;
};

struct pcpu_seg6_local_counters {
        u64_stats_t packets;
        u64_stats_t bytes;
        u64_stats_t errors;

        struct u64_stats_sync syncp;
};

/* This struct groups all the SRv6 Behavior counters supported so far.
 *
 * put_nla_counters() makes use of this data structure to collect all counter
 * values after the per-CPU counter evaluation has been performed.
 * Finally, each counter value (in seg6_local_counters) is stored in the
 * corresponding netlink attribute and sent to user space.
 *
 * NB: we don't want to expose this structure to user space!
 */
struct seg6_local_counters {
        __u64 packets;
        __u64 bytes;
        __u64 errors;
};

#define seg6_local_alloc_pcpu_counters(__gfp)                           \
        __netdev_alloc_pcpu_stats(struct pcpu_seg6_local_counters,      \
                                  ((__gfp) | __GFP_ZERO))

#define SEG6_F_LOCAL_COUNTERS   SEG6_F_ATTR(SEG6_LOCAL_COUNTERS)

struct seg6_local_lwt {
        int action;
        struct ipv6_sr_hdr *srh;
        int table;
        struct in_addr nh4;
        struct in6_addr nh6;
        int iif;
        int oif;
        struct bpf_lwt_prog bpf;
#ifdef CONFIG_NET_L3_MASTER_DEV
        struct seg6_end_dt_info dt_info;
#endif
        struct seg6_flavors_info flv_info;

        struct pcpu_seg6_local_counters __percpu *pcpu_counters;

        int headroom;
        struct seg6_action_desc *desc;
        /* unlike the required attrs, we have to track the optional attributes
         * that have been effectively parsed.
         */
        unsigned long parsed_optattrs;
};

static struct seg6_local_lwt *seg6_local_lwtunnel(struct lwtunnel_state *lwt)
{
        return (struct seg6_local_lwt *)lwt->data;
}

static struct ipv6_sr_hdr *get_and_validate_srh(struct sk_buff *skb)
{
        struct ipv6_sr_hdr *srh;

        srh = seg6_get_srh(skb, IP6_FH_F_SKIP_RH);
        if (!srh)
                return NULL;

#ifdef CONFIG_IPV6_SEG6_HMAC
        if (!seg6_hmac_validate_skb(skb))
                return NULL;
#endif

        return srh;
}

static bool decap_and_validate(struct sk_buff *skb, int proto)
{
        struct ipv6_sr_hdr *srh;
        unsigned int off = 0;

        srh = seg6_get_srh(skb, 0);
        if (srh && srh->segments_left > 0)
                return false;

#ifdef CONFIG_IPV6_SEG6_HMAC
        if (srh && !seg6_hmac_validate_skb(skb))
                return false;
#endif

        if (ipv6_find_hdr(skb, &off, proto, NULL, NULL) < 0)
                return false;

        if (!pskb_pull(skb, off))
                return false;

        skb_postpull_rcsum(skb, skb_network_header(skb), off);

        skb_reset_network_header(skb);
        skb_reset_transport_header(skb);
        if (iptunnel_pull_offloads(skb))
                return false;

        return true;
}

static void advance_nextseg(struct ipv6_sr_hdr *srh, struct in6_addr *daddr)
{
        struct in6_addr *addr;

        srh->segments_left--;
        addr = srh->segments + srh->segments_left;
        *daddr = *addr;
}

static int
seg6_lookup_any_nexthop(struct sk_buff *skb, struct in6_addr *nhaddr,
                        u32 tbl_id, bool local_delivery, int oif)
{
        struct net *net = dev_net(skb->dev);
        struct ipv6hdr *hdr = ipv6_hdr(skb);
        int flags = RT6_LOOKUP_F_HAS_SADDR;
        struct dst_entry *dst = NULL;
        struct rt6_info *rt;
        struct flowi6 fl6;
        int dev_flags = 0;

        memset(&fl6, 0, sizeof(fl6));
        fl6.flowi6_iif = skb->dev->ifindex;
        fl6.flowi6_oif = oif;
        fl6.daddr = nhaddr ? *nhaddr : hdr->daddr;
        fl6.saddr = hdr->saddr;
        fl6.flowlabel = ip6_flowinfo(hdr);
        fl6.flowi6_mark = skb->mark;
        fl6.flowi6_proto = hdr->nexthdr;

        if (nhaddr)
                fl6.flowi6_flags = FLOWI_FLAG_KNOWN_NH;

        if (!tbl_id && !oif) {
                dst = ip6_route_input_lookup(net, skb->dev, &fl6, skb, flags);
        } else if (tbl_id) {
                struct fib6_table *table;

                table = fib6_get_table(net, tbl_id);
                if (!table)
                        goto out;

                rt = ip6_pol_route(net, table, oif, &fl6, skb, flags);
                dst = &rt->dst;
        } else {
                dst = ip6_route_output(net, NULL, &fl6);
        }

        /* we want to discard traffic destined for local packet processing,
         * if @local_delivery is set to false.
         */
        if (!local_delivery)
                dev_flags |= IFF_LOOPBACK;

        if (dst && (dst_dev(dst)->flags & dev_flags) && !dst->error) {
                dst_release(dst);
                dst = NULL;
        }

out:
        if (!dst) {
                rt = net->ipv6.ip6_blk_hole_entry;
                dst = &rt->dst;
                dst_hold(dst);
        }

        skb_dst_drop(skb);
        skb_dst_set(skb, dst);
        return dst->error;
}

int seg6_lookup_nexthop(struct sk_buff *skb,
                        struct in6_addr *nhaddr, u32 tbl_id)
{
        return seg6_lookup_any_nexthop(skb, nhaddr, tbl_id, false, 0);
}

static __u8 seg6_flv_lcblock_octects(const struct seg6_flavors_info *finfo)
{
        return finfo->lcblock_bits >> 3;
}

static __u8 seg6_flv_lcnode_func_octects(const struct seg6_flavors_info *finfo)
{
        return finfo->lcnode_func_bits >> 3;
}

static bool seg6_next_csid_is_arg_zero(const struct in6_addr *addr,
                                       const struct seg6_flavors_info *finfo)
{
        __u8 fnc_octects = seg6_flv_lcnode_func_octects(finfo);
        __u8 blk_octects = seg6_flv_lcblock_octects(finfo);
        __u8 arg_octects;
        int i;

        arg_octects = 16 - blk_octects - fnc_octects;
        for (i = 0; i < arg_octects; ++i) {
                if (addr->s6_addr[blk_octects + fnc_octects + i] != 0x00)
                        return false;
        }

        return true;
}

/* assume that DA.Argument length > 0 */
static void seg6_next_csid_advance_arg(struct in6_addr *addr,
                                       const struct seg6_flavors_info *finfo)
{
        __u8 fnc_octects = seg6_flv_lcnode_func_octects(finfo);
        __u8 blk_octects = seg6_flv_lcblock_octects(finfo);

        /* advance DA.Argument */
        memmove(&addr->s6_addr[blk_octects],
                &addr->s6_addr[blk_octects + fnc_octects],
                16 - blk_octects - fnc_octects);

        memset(&addr->s6_addr[16 - fnc_octects], 0x00, fnc_octects);
}

static int input_action_end_finish(struct sk_buff *skb,
                                   struct seg6_local_lwt *slwt)
{
        seg6_lookup_nexthop(skb, NULL, 0);

        return dst_input(skb);
}

static int input_action_end_core(struct sk_buff *skb,
                                 struct seg6_local_lwt *slwt)
{
        struct ipv6_sr_hdr *srh;

        srh = get_and_validate_srh(skb);
        if (!srh)
                goto drop;

        advance_nextseg(srh, &ipv6_hdr(skb)->daddr);

        return input_action_end_finish(skb, slwt);

drop:
        kfree_skb(skb);
        return -EINVAL;
}

static int end_next_csid_core(struct sk_buff *skb, struct seg6_local_lwt *slwt)
{
        const struct seg6_flavors_info *finfo = &slwt->flv_info;
        struct in6_addr *daddr = &ipv6_hdr(skb)->daddr;

        if (seg6_next_csid_is_arg_zero(daddr, finfo))
                return input_action_end_core(skb, slwt);

        /* update DA */
        seg6_next_csid_advance_arg(daddr, finfo);

        return input_action_end_finish(skb, slwt);
}

static int input_action_end_x_finish(struct sk_buff *skb,
                                     struct seg6_local_lwt *slwt)
{
        seg6_lookup_any_nexthop(skb, &slwt->nh6, 0, false, slwt->oif);

        return dst_input(skb);
}

static int input_action_end_x_core(struct sk_buff *skb,
                                   struct seg6_local_lwt *slwt)
{
        struct ipv6_sr_hdr *srh;

        srh = get_and_validate_srh(skb);
        if (!srh)
                goto drop;

        advance_nextseg(srh, &ipv6_hdr(skb)->daddr);

        return input_action_end_x_finish(skb, slwt);

drop:
        kfree_skb(skb);
        return -EINVAL;
}

static int end_x_next_csid_core(struct sk_buff *skb,
                                struct seg6_local_lwt *slwt)
{
        const struct seg6_flavors_info *finfo = &slwt->flv_info;
        struct in6_addr *daddr = &ipv6_hdr(skb)->daddr;

        if (seg6_next_csid_is_arg_zero(daddr, finfo))
                return input_action_end_x_core(skb, slwt);

        /* update DA */
        seg6_next_csid_advance_arg(daddr, finfo);

        return input_action_end_x_finish(skb, slwt);
}

static bool seg6_next_csid_enabled(__u32 fops)
{
        return fops & SEG6_F_LOCAL_FLV_NEXT_CSID;
}

/* Processing of SRv6 End, End.X, and End.T behaviors can be extended through
 * the flavors framework. These behaviors must report the subset of (flavor)
 * operations they currently implement. In this way, if a user specifies a
 * flavor combination that is not supported by a given End* behavior, the
 * kernel refuses to instantiate the tunnel reporting the error.
 */
static int seg6_flv_supp_ops_by_action(int action, __u32 *fops)
{
        switch (action) {
        case SEG6_LOCAL_ACTION_END:
                *fops = SEG6_LOCAL_END_FLV_SUPP_OPS;
                break;
        case SEG6_LOCAL_ACTION_END_X:
                *fops = SEG6_LOCAL_END_X_FLV_SUPP_OPS;
                break;
        default:
                return -EOPNOTSUPP;
        }

        return 0;
}

/* We describe the packet state in relation to the absence/presence of the SRH
 * and the Segment Left (SL) field.
 * For our purposes, it is not necessary to record the exact value of the SL
 * when the SID List consists of two or more segments.
 */
enum seg6_local_pktinfo {
        /* the order really matters! */
        SEG6_LOCAL_PKTINFO_NOHDR        = 0,
        SEG6_LOCAL_PKTINFO_SL_ZERO,
        SEG6_LOCAL_PKTINFO_SL_ONE,
        SEG6_LOCAL_PKTINFO_SL_MORE,
        __SEG6_LOCAL_PKTINFO_MAX,
};

#define SEG6_LOCAL_PKTINFO_MAX (__SEG6_LOCAL_PKTINFO_MAX - 1)

static enum seg6_local_pktinfo seg6_get_srh_pktinfo(struct ipv6_sr_hdr *srh)
{
        __u8 sgl;

        if (!srh)
                return SEG6_LOCAL_PKTINFO_NOHDR;

        sgl = srh->segments_left;
        if (sgl < 2)
                return SEG6_LOCAL_PKTINFO_SL_ZERO + sgl;

        return SEG6_LOCAL_PKTINFO_SL_MORE;
}

enum seg6_local_flv_action {
        SEG6_LOCAL_FLV_ACT_UNSPEC       = 0,
        SEG6_LOCAL_FLV_ACT_END,
        SEG6_LOCAL_FLV_ACT_PSP,
        SEG6_LOCAL_FLV_ACT_USP,
        SEG6_LOCAL_FLV_ACT_USD,
        __SEG6_LOCAL_FLV_ACT_MAX
};

#define SEG6_LOCAL_FLV_ACT_MAX (__SEG6_LOCAL_FLV_ACT_MAX - 1)

/* The action table for RFC8986 flavors (see the flv8986_act_tbl below)
 * contains the actions (i.e. processing operations) to be applied on packets
 * when flavors are configured for an End* behavior.
 * By combining the pkinfo data and from the flavors mask, the macro
 * computes the index used to access the elements (actions) stored in the
 * action table. The index is structured as follows:
 *
 *                     index
 *       _______________/\________________
 *      /                                 \
 *      +----------------+----------------+
 *      |        pf      |      afm       |
 *      +----------------+----------------+
 *        ph-1 ... p1 p0   fk-1 ... f1 f0
 *     MSB                               LSB
 *
 * where:
 *  - 'afm' (adjusted flavor mask) is the mask containing a combination of the
 *     RFC8986 flavors currently supported. 'afm' corresponds to the @fm
 *     argument of the macro whose value is righ-shifted by 1 bit. By doing so,
 *     we discard the SEG6_LOCAL_FLV_OP_UNSPEC flag (bit 0 in @fm) which is
 *     never used here;
 *  - 'pf' encodes the packet info (pktinfo) regarding the presence/absence of
 *    the SRH, SL = 0, etc. 'pf' is set with the value of @pf provided as
 *    argument to the macro.
 */
#define flv8986_act_tbl_idx(pf, fm)                                     \
        ((((pf) << bits_per(SEG6_LOCAL_FLV8986_SUPP_OPS)) |             \
          ((fm) & SEG6_LOCAL_FLV8986_SUPP_OPS)) >> SEG6_LOCAL_FLV_OP_PSP)

/* We compute the size of the action table by considering the RFC8986 flavors
 * actually supported by the kernel. In this way, the size is automatically
 * adjusted when new flavors are supported.
 */
#define FLV8986_ACT_TBL_SIZE                                            \
        roundup_pow_of_two(flv8986_act_tbl_idx(SEG6_LOCAL_PKTINFO_MAX,  \
                                               SEG6_LOCAL_FLV8986_SUPP_OPS))

/* tbl_cfg(act, pf, fm) macro is used to easily configure the action
 * table; it accepts 3 arguments:
 *     i) @act, the suffix from SEG6_LOCAL_FLV_ACT_{act} representing
 *        the action that should be applied on the packet;
 *    ii) @pf, the suffix from SEG6_LOCAL_PKTINFO_{pf} reporting the packet
 *        info about the lack/presence of SRH, SRH with SL = 0, etc;
 *   iii) @fm, the mask of flavors.
 */
#define tbl_cfg(act, pf, fm)                                            \
        [flv8986_act_tbl_idx(SEG6_LOCAL_PKTINFO_##pf,                   \
                             (fm))] = SEG6_LOCAL_FLV_ACT_##act

/* shorthand for improving readability */
#define F_PSP   SEG6_F_LOCAL_FLV_PSP

/* The table contains, for each combination of the pktinfo data and
 * flavors, the action that should be taken on a packet (e.g.
 * "standard" Endpoint processing, Penultimate Segment Pop, etc).
 *
 * By default, table entries not explicitly configured are initialized with the
 * SEG6_LOCAL_FLV_ACT_UNSPEC action, which generally has the effect of
 * discarding the processed packet.
 */
static const u8 flv8986_act_tbl[FLV8986_ACT_TBL_SIZE] = {
        /* PSP variant for packet where SRH with SL = 1 */
        tbl_cfg(PSP, SL_ONE, F_PSP),
        /* End for packet where the SRH with SL > 1*/
        tbl_cfg(END, SL_MORE, F_PSP),
};

#undef F_PSP
#undef tbl_cfg

/* For each flavor defined in RFC8986 (or a combination of them) an action is
 * performed on the packet. The specific action depends on:
 *  - info extracted from the packet (i.e. pktinfo data) regarding the
 *    lack/presence of the SRH, and if the SRH is available, on the value of
 *    Segment Left field;
 *  - the mask of flavors configured for the specific SRv6 End* behavior.
 *
 * The function combines both the pkinfo and the flavors mask to evaluate the
 * corresponding action to be taken on the packet.
 */
static enum seg6_local_flv_action
seg6_local_flv8986_act_lookup(enum seg6_local_pktinfo pinfo, __u32 flvmask)
{
        unsigned long index;

        /* check if the provided mask of flavors is supported */
        if (unlikely(flvmask & ~SEG6_LOCAL_FLV8986_SUPP_OPS))
                return SEG6_LOCAL_FLV_ACT_UNSPEC;

        index = flv8986_act_tbl_idx(pinfo, flvmask);
        if (unlikely(index >= FLV8986_ACT_TBL_SIZE))
                return SEG6_LOCAL_FLV_ACT_UNSPEC;

        return flv8986_act_tbl[index];
}

/* skb->data must be aligned with skb->network_header */
static bool seg6_pop_srh(struct sk_buff *skb, int srhoff)
{
        struct ipv6_sr_hdr *srh;
        struct ipv6hdr *iph;
        __u8 srh_nexthdr;
        int thoff = -1;
        int srhlen;
        int nhlen;

        if (unlikely(srhoff < sizeof(*iph) ||
                     !pskb_may_pull(skb, srhoff + sizeof(*srh))))
                return false;

        srh = (struct ipv6_sr_hdr *)(skb->data + srhoff);
        srhlen = ipv6_optlen(srh);

        /* we are about to mangle the pkt, let's check if we can write on it */
        if (unlikely(skb_ensure_writable(skb, srhoff + srhlen)))
                return false;

        /* skb_ensure_writable() may change skb pointers; evaluate srh again */
        srh = (struct ipv6_sr_hdr *)(skb->data + srhoff);
        srh_nexthdr = srh->nexthdr;

        if (unlikely(!skb_transport_header_was_set(skb)))
                goto pull;

        nhlen = skb_network_header_len(skb);
        /* we have to deal with the transport header: it could be set before
         * the SRH, after the SRH, or within it (which is considered wrong,
         * however).
         */
        if (likely(nhlen <= srhoff))
                thoff = nhlen;
        else if (nhlen >= srhoff + srhlen)
                /* transport_header is set after the SRH */
                thoff = nhlen - srhlen;
        else
                /* transport_header falls inside the SRH; hence, we can't
                 * restore the transport_header pointer properly after
                 * SRH removing operation.
                 */
                return false;
pull:
        /* we need to pop the SRH:
         *  1) first of all, we pull out everything from IPv6 header up to SRH
         *     (included) evaluating also the rcsum;
         *  2) we overwrite (and then remove) the SRH by properly moving the
         *     IPv6 along with any extension header that precedes the SRH;
         *  3) At the end, we push back the pulled headers (except for SRH,
         *     obviously).
         */
        skb_pull_rcsum(skb, srhoff + srhlen);
        memmove(skb_network_header(skb) + srhlen, skb_network_header(skb),
                srhoff);
        skb_push(skb, srhoff);

        skb_reset_network_header(skb);
        skb_mac_header_rebuild(skb);
        if (likely(thoff >= 0))
                skb_set_transport_header(skb, thoff);

        iph = ipv6_hdr(skb);
        if (iph->nexthdr == NEXTHDR_ROUTING) {
                iph->nexthdr = srh_nexthdr;
        } else {
                /* we must look for the extension header (EXTH, for short) that
                 * immediately precedes the SRH we have just removed.
                 * Then, we update the value of the EXTH nexthdr with the one
                 * contained in the SRH nexthdr.
                 */
                unsigned int off = sizeof(*iph);
                struct ipv6_opt_hdr *hp, _hdr;
                __u8 nexthdr = iph->nexthdr;

                for (;;) {
                        if (unlikely(!ipv6_ext_hdr(nexthdr) ||
                                     nexthdr == NEXTHDR_NONE))
                                return false;

                        hp = skb_header_pointer(skb, off, sizeof(_hdr), &_hdr);
                        if (unlikely(!hp))
                                return false;

                        if (hp->nexthdr == NEXTHDR_ROUTING) {
                                hp->nexthdr = srh_nexthdr;
                                break;
                        }

                        switch (nexthdr) {
                        case NEXTHDR_FRAGMENT:
                                fallthrough;
                        case NEXTHDR_AUTH:
                                /* we expect SRH before FRAG and AUTH */
                                return false;
                        default:
                                off += ipv6_optlen(hp);
                                break;
                        }

                        nexthdr = hp->nexthdr;
                }
        }

        iph->payload_len = htons(skb->len - sizeof(struct ipv6hdr));

        skb_postpush_rcsum(skb, iph, srhoff);

        return true;
}

/* process the packet on the basis of the RFC8986 flavors set for the given
 * SRv6 End behavior instance.
 */
static int end_flv8986_core(struct sk_buff *skb, struct seg6_local_lwt *slwt)
{
        const struct seg6_flavors_info *finfo = &slwt->flv_info;
        enum seg6_local_flv_action action;
        enum seg6_local_pktinfo pinfo;
        struct ipv6_sr_hdr *srh;
        __u32 flvmask;
        int srhoff;

        srh = seg6_get_srh(skb, 0);
        srhoff = srh ? ((unsigned char *)srh - skb->data) : 0;
        pinfo = seg6_get_srh_pktinfo(srh);
#ifdef CONFIG_IPV6_SEG6_HMAC
        if (srh && !seg6_hmac_validate_skb(skb))
                goto drop;
#endif
        flvmask = finfo->flv_ops;
        if (unlikely(flvmask & ~SEG6_LOCAL_FLV8986_SUPP_OPS)) {
                pr_warn_once("seg6local: invalid RFC8986 flavors\n");
                goto drop;
        }

        /* retrieve the action triggered by the combination of pktinfo data and
         * the flavors mask.
         */
        action = seg6_local_flv8986_act_lookup(pinfo, flvmask);
        switch (action) {
        case SEG6_LOCAL_FLV_ACT_END:
                /* process the packet as the "standard" End behavior */
                advance_nextseg(srh, &ipv6_hdr(skb)->daddr);
                break;
        case SEG6_LOCAL_FLV_ACT_PSP:
                advance_nextseg(srh, &ipv6_hdr(skb)->daddr);

                if (unlikely(!seg6_pop_srh(skb, srhoff)))
                        goto drop;
                break;
        case SEG6_LOCAL_FLV_ACT_UNSPEC:
                fallthrough;
        default:
                /* by default, we drop the packet since we could not find a
                 * suitable action.
                 */
                goto drop;
        }

        return input_action_end_finish(skb, slwt);

drop:
        kfree_skb(skb);
        return -EINVAL;
}

/* regular endpoint function */
static int input_action_end(struct sk_buff *skb, struct seg6_local_lwt *slwt)
{
        const struct seg6_flavors_info *finfo = &slwt->flv_info;
        __u32 fops = finfo->flv_ops;

        if (!fops)
                return input_action_end_core(skb, slwt);

        /* check for the presence of NEXT-C-SID since it applies first */
        if (seg6_next_csid_enabled(fops))
                return end_next_csid_core(skb, slwt);

        /* the specific processing function to be performed on the packet
         * depends on the combination of flavors defined in RFC8986 and some
         * information extracted from the packet, e.g. presence/absence of SRH,
         * Segment Left = 0, etc.
         */
        return end_flv8986_core(skb, slwt);
}

/* regular endpoint, and forward to specified nexthop */
static int input_action_end_x(struct sk_buff *skb, struct seg6_local_lwt *slwt)
{
        const struct seg6_flavors_info *finfo = &slwt->flv_info;
        __u32 fops = finfo->flv_ops;

        /* check for the presence of NEXT-C-SID since it applies first */
        if (seg6_next_csid_enabled(fops))
                return end_x_next_csid_core(skb, slwt);

        return input_action_end_x_core(skb, slwt);
}

static int input_action_end_t(struct sk_buff *skb, struct seg6_local_lwt *slwt)
{
        struct ipv6_sr_hdr *srh;

        srh = get_and_validate_srh(skb);
        if (!srh)
                goto drop;

        advance_nextseg(srh, &ipv6_hdr(skb)->daddr);

        seg6_lookup_nexthop(skb, NULL, slwt->table);

        return dst_input(skb);

drop:
        kfree_skb(skb);
        return -EINVAL;
}

/* decapsulate and forward inner L2 frame on specified interface */
static int input_action_end_dx2(struct sk_buff *skb,
                                struct seg6_local_lwt *slwt)
{
        struct net *net = dev_net(skb->dev);
        struct net_device *odev;
        struct ethhdr *eth;

        if (!decap_and_validate(skb, IPPROTO_ETHERNET))
                goto drop;

        if (!pskb_may_pull(skb, ETH_HLEN))
                goto drop;

        skb_reset_mac_header(skb);
        eth = (struct ethhdr *)skb->data;

        /* To determine the frame's protocol, we assume it is 802.3. This avoids
         * a call to eth_type_trans(), which is not really relevant for our
         * use case.
         */
        if (!eth_proto_is_802_3(eth->h_proto))
                goto drop;

        odev = dev_get_by_index_rcu(net, slwt->oif);
        if (!odev)
                goto drop;

        /* As we accept Ethernet frames, make sure the egress device is of
         * the correct type.
         */
        if (odev->type != ARPHRD_ETHER)
                goto drop;

        if (!(odev->flags & IFF_UP) || !netif_carrier_ok(odev))
                goto drop;

        skb_orphan(skb);

        if (skb_warn_if_lro(skb))
                goto drop;

        skb_forward_csum(skb);

        if (skb->len - ETH_HLEN > odev->mtu)
                goto drop;

        skb->dev = odev;
        skb->protocol = eth->h_proto;

        return dev_queue_xmit(skb);

drop:
        kfree_skb(skb);
        return -EINVAL;
}

static int input_action_end_dx6_finish(struct net *net, struct sock *sk,
                                       struct sk_buff *skb)
{
        struct dst_entry *orig_dst = skb_dst(skb);
        struct in6_addr *nhaddr = NULL;
        struct seg6_local_lwt *slwt;

        slwt = seg6_local_lwtunnel(orig_dst->lwtstate);

        /* The inner packet is not associated to any local interface,
         * so we do not call netif_rx().
         *
         * If slwt->nh6 is set to ::, then lookup the nexthop for the
         * inner packet's DA. Otherwise, use the specified nexthop.
         */
        if (!ipv6_addr_any(&slwt->nh6))
                nhaddr = &slwt->nh6;

        seg6_lookup_nexthop(skb, nhaddr, 0);

        return dst_input(skb);
}

/* decapsulate and forward to specified nexthop */
static int input_action_end_dx6(struct sk_buff *skb,
                                struct seg6_local_lwt *slwt)
{
        /* this function accepts IPv6 encapsulated packets, with either
         * an SRH with SL=0, or no SRH.
         */

        if (!decap_and_validate(skb, IPPROTO_IPV6))
                goto drop;

        if (!pskb_may_pull(skb, sizeof(struct ipv6hdr)))
                goto drop;

        skb_set_transport_header(skb, sizeof(struct ipv6hdr));
        nf_reset_ct(skb);

        if (static_branch_unlikely(&nf_hooks_lwtunnel_enabled))
                return NF_HOOK(NFPROTO_IPV6, NF_INET_PRE_ROUTING,
                               dev_net(skb->dev), NULL, skb, skb->dev,
                               NULL, input_action_end_dx6_finish);

        return input_action_end_dx6_finish(dev_net(skb->dev), NULL, skb);
drop:
        kfree_skb(skb);
        return -EINVAL;
}

static int input_action_end_dx4_finish(struct net *net, struct sock *sk,
                                       struct sk_buff *skb)
{
        struct dst_entry *orig_dst = skb_dst(skb);
        enum skb_drop_reason reason;
        struct seg6_local_lwt *slwt;
        struct iphdr *iph;
        __be32 nhaddr;

        slwt = seg6_local_lwtunnel(orig_dst->lwtstate);

        iph = ip_hdr(skb);

        nhaddr = slwt->nh4.s_addr ?: iph->daddr;

        skb_dst_drop(skb);

        reason = ip_route_input(skb, nhaddr, iph->saddr, 0, skb->dev);
        if (reason) {
                kfree_skb_reason(skb, reason);
                return -EINVAL;
        }

        return dst_input(skb);
}

static int input_action_end_dx4(struct sk_buff *skb,
                                struct seg6_local_lwt *slwt)
{
        if (!decap_and_validate(skb, IPPROTO_IPIP))
                goto drop;

        if (!pskb_may_pull(skb, sizeof(struct iphdr)))
                goto drop;

        skb->protocol = htons(ETH_P_IP);
        skb_set_transport_header(skb, sizeof(struct iphdr));
        nf_reset_ct(skb);

        if (static_branch_unlikely(&nf_hooks_lwtunnel_enabled))
                return NF_HOOK(NFPROTO_IPV4, NF_INET_PRE_ROUTING,
                               dev_net(skb->dev), NULL, skb, skb->dev,
                               NULL, input_action_end_dx4_finish);

        return input_action_end_dx4_finish(dev_net(skb->dev), NULL, skb);
drop:
        kfree_skb(skb);
        return -EINVAL;
}

#ifdef CONFIG_NET_L3_MASTER_DEV
static struct net *fib6_config_get_net(const struct fib6_config *fib6_cfg)
{
        const struct nl_info *nli = &fib6_cfg->fc_nlinfo;

        return nli->nl_net;
}

static int __seg6_end_dt_vrf_build(struct seg6_local_lwt *slwt, const void *cfg,
                                   u16 family, struct netlink_ext_ack *extack)
{
        struct seg6_end_dt_info *info = &slwt->dt_info;
        int vrf_ifindex;
        struct net *net;

        net = fib6_config_get_net(cfg);

        /* note that vrf_table was already set by parse_nla_vrftable() */
        vrf_ifindex = l3mdev_ifindex_lookup_by_table_id(L3MDEV_TYPE_VRF, net,
                                                        info->vrf_table);
        if (vrf_ifindex < 0) {
                if (vrf_ifindex == -EPERM) {
                        NL_SET_ERR_MSG(extack,
                                       "Strict mode for VRF is disabled");
                } else if (vrf_ifindex == -ENODEV) {
                        NL_SET_ERR_MSG(extack,
                                       "Table has no associated VRF device");
                } else {
                        pr_debug("seg6local: SRv6 End.DT* creation error=%d\n",
                                 vrf_ifindex);
                }

                return vrf_ifindex;
        }

        info->net = net;
        info->vrf_ifindex = vrf_ifindex;

        info->family = family;
        info->mode = DT_VRF_MODE;

        return 0;
}

/* The SRv6 End.DT4/DT6 behavior extracts the inner (IPv4/IPv6) packet and
 * routes the IPv4/IPv6 packet by looking at the configured routing table.
 *
 * In the SRv6 End.DT4/DT6 use case, we can receive traffic (IPv6+Segment
 * Routing Header packets) from several interfaces and the outer IPv6
 * destination address (DA) is used for retrieving the specific instance of the
 * End.DT4/DT6 behavior that should process the packets.
 *
 * However, the inner IPv4/IPv6 packet is not really bound to any receiving
 * interface and thus the End.DT4/DT6 sets the VRF (associated with the
 * corresponding routing table) as the *receiving* interface.
 * In other words, the End.DT4/DT6 processes a packet as if it has been received
 * directly by the VRF (and not by one of its slave devices, if any).
 * In this way, the VRF interface is used for routing the IPv4/IPv6 packet in
 * according to the routing table configured by the End.DT4/DT6 instance.
 *
 * This design allows you to get some interesting features like:
 *  1) the statistics on rx packets;
 *  2) the possibility to install a packet sniffer on the receiving interface
 *     (the VRF one) for looking at the incoming packets;
 *  3) the possibility to leverage the netfilter prerouting hook for the inner
 *     IPv4 packet.
 *
 * This function returns:
 *  - the sk_buff* when the VRF rcv handler has processed the packet correctly;
 *  - NULL when the skb is consumed by the VRF rcv handler;
 *  - a pointer which encodes a negative error number in case of error.
 *    Note that in this case, the function takes care of freeing the skb.
 */
static struct sk_buff *end_dt_vrf_rcv(struct sk_buff *skb, u16 family,
                                      struct net_device *dev)
{
        /* based on l3mdev_ip_rcv; we are only interested in the master */
        if (unlikely(!netif_is_l3_master(dev) && !netif_has_l3_rx_handler(dev)))
                goto drop;

        if (unlikely(!dev->l3mdev_ops->l3mdev_l3_rcv))
                goto drop;

        /* the decap packet IPv4/IPv6 does not come with any mac header info.
         * We must unset the mac header to allow the VRF device to rebuild it,
         * just in case there is a sniffer attached on the device.
         */
        skb_unset_mac_header(skb);

        skb = dev->l3mdev_ops->l3mdev_l3_rcv(dev, skb, family);
        if (!skb)
                /* the skb buffer was consumed by the handler */
                return NULL;

        /* when a packet is received by a VRF or by one of its slaves, the
         * master device reference is set into the skb.
         */
        if (unlikely(skb->dev != dev || skb->skb_iif != dev->ifindex))
                goto drop;

        return skb;

drop:
        kfree_skb(skb);
        return ERR_PTR(-EINVAL);
}

static struct net_device *end_dt_get_vrf_rcu(struct sk_buff *skb,
                                             struct seg6_end_dt_info *info)
{
        int vrf_ifindex = info->vrf_ifindex;
        struct net *net = info->net;

        if (unlikely(vrf_ifindex < 0))
                goto error;

        if (unlikely(!net_eq(dev_net(skb->dev), net)))
                goto error;

        return dev_get_by_index_rcu(net, vrf_ifindex);

error:
        return NULL;
}

static struct sk_buff *end_dt_vrf_core(struct sk_buff *skb,
                                       struct seg6_local_lwt *slwt, u16 family)
{
        struct seg6_end_dt_info *info = &slwt->dt_info;
        struct net_device *vrf;
        __be16 protocol;
        int hdrlen;

        vrf = end_dt_get_vrf_rcu(skb, info);
        if (unlikely(!vrf))
                goto drop;

        switch (family) {
        case AF_INET:
                protocol = htons(ETH_P_IP);
                hdrlen = sizeof(struct iphdr);
                break;
        case AF_INET6:
                protocol = htons(ETH_P_IPV6);
                hdrlen = sizeof(struct ipv6hdr);
                break;
        case AF_UNSPEC:
                fallthrough;
        default:
                goto drop;
        }

        if (unlikely(info->family != AF_UNSPEC && info->family != family)) {
                pr_warn_once("seg6local: SRv6 End.DT* family mismatch");
                goto drop;
        }

        skb->protocol = protocol;

        skb_dst_drop(skb);

        skb_set_transport_header(skb, hdrlen);
        nf_reset_ct(skb);

        return end_dt_vrf_rcv(skb, family, vrf);

drop:
        kfree_skb(skb);
        return ERR_PTR(-EINVAL);
}

static int input_action_end_dt4(struct sk_buff *skb,
                                struct seg6_local_lwt *slwt)
{
        enum skb_drop_reason reason;
        struct iphdr *iph;

        if (!decap_and_validate(skb, IPPROTO_IPIP))
                goto drop;

        if (!pskb_may_pull(skb, sizeof(struct iphdr)))
                goto drop;

        skb = end_dt_vrf_core(skb, slwt, AF_INET);
        if (!skb)
                /* packet has been processed and consumed by the VRF */
                return 0;

        if (IS_ERR(skb))
                return PTR_ERR(skb);

        iph = ip_hdr(skb);

        reason = ip_route_input(skb, iph->daddr, iph->saddr, 0, skb->dev);
        if (unlikely(reason))
                goto drop;

        return dst_input(skb);

drop:
        kfree_skb(skb);
        return -EINVAL;
}

static int seg6_end_dt4_build(struct seg6_local_lwt *slwt, const void *cfg,
                              struct netlink_ext_ack *extack)
{
        return __seg6_end_dt_vrf_build(slwt, cfg, AF_INET, extack);
}

static enum
seg6_end_dt_mode seg6_end_dt6_parse_mode(struct seg6_local_lwt *slwt)
{
        unsigned long parsed_optattrs = slwt->parsed_optattrs;
        bool legacy, vrfmode;

        legacy  = !!(parsed_optattrs & SEG6_F_ATTR(SEG6_LOCAL_TABLE));
        vrfmode = !!(parsed_optattrs & SEG6_F_ATTR(SEG6_LOCAL_VRFTABLE));

        if (!(legacy ^ vrfmode))
                /* both are absent or present: invalid DT6 mode */
                return DT_INVALID_MODE;

        return legacy ? DT_LEGACY_MODE : DT_VRF_MODE;
}

static enum seg6_end_dt_mode seg6_end_dt6_get_mode(struct seg6_local_lwt *slwt)
{
        struct seg6_end_dt_info *info = &slwt->dt_info;

        return info->mode;
}

static int seg6_end_dt6_build(struct seg6_local_lwt *slwt, const void *cfg,
                              struct netlink_ext_ack *extack)
{
        enum seg6_end_dt_mode mode = seg6_end_dt6_parse_mode(slwt);
        struct seg6_end_dt_info *info = &slwt->dt_info;

        switch (mode) {
        case DT_LEGACY_MODE:
                info->mode = DT_LEGACY_MODE;
                return 0;
        case DT_VRF_MODE:
                return __seg6_end_dt_vrf_build(slwt, cfg, AF_INET6, extack);
        default:
                NL_SET_ERR_MSG(extack, "table or vrftable must be specified");
                return -EINVAL;
        }
}
#endif

static int input_action_end_dt6(struct sk_buff *skb,
                                struct seg6_local_lwt *slwt)
{
        if (!decap_and_validate(skb, IPPROTO_IPV6))
                goto drop;

        if (!pskb_may_pull(skb, sizeof(struct ipv6hdr)))
                goto drop;

#ifdef CONFIG_NET_L3_MASTER_DEV
        if (seg6_end_dt6_get_mode(slwt) == DT_LEGACY_MODE)
                goto legacy_mode;

        /* DT6_VRF_MODE */
        skb = end_dt_vrf_core(skb, slwt, AF_INET6);
        if (!skb)
                /* packet has been processed and consumed by the VRF */
                return 0;

        if (IS_ERR(skb))
                return PTR_ERR(skb);

        /* note: this time we do not need to specify the table because the VRF
         * takes care of selecting the correct table.
         */
        seg6_lookup_any_nexthop(skb, NULL, 0, true, 0);

        return dst_input(skb);

legacy_mode:
#endif
        skb_set_transport_header(skb, sizeof(struct ipv6hdr));

        seg6_lookup_any_nexthop(skb, NULL, slwt->table, true, 0);

        return dst_input(skb);

drop:
        kfree_skb(skb);
        return -EINVAL;
}

#ifdef CONFIG_NET_L3_MASTER_DEV
static int seg6_end_dt46_build(struct seg6_local_lwt *slwt, const void *cfg,
                               struct netlink_ext_ack *extack)
{
        return __seg6_end_dt_vrf_build(slwt, cfg, AF_UNSPEC, extack);
}

static int input_action_end_dt46(struct sk_buff *skb,
                                 struct seg6_local_lwt *slwt)
{
        unsigned int off = 0;
        int nexthdr;

        nexthdr = ipv6_find_hdr(skb, &off, -1, NULL, NULL);
        if (unlikely(nexthdr < 0))
                goto drop;

        switch (nexthdr) {
        case IPPROTO_IPIP:
                return input_action_end_dt4(skb, slwt);
        case IPPROTO_IPV6:
                return input_action_end_dt6(skb, slwt);
        }

drop:
        kfree_skb(skb);
        return -EINVAL;
}
#endif

/* push an SRH on top of the current one */
static int input_action_end_b6(struct sk_buff *skb, struct seg6_local_lwt *slwt)
{
        struct ipv6_sr_hdr *srh;
        int err = -EINVAL;

        srh = get_and_validate_srh(skb);
        if (!srh)
                goto drop;

        err = seg6_do_srh_inline(skb, slwt->srh);
        if (err)
                goto drop;

        skb_set_transport_header(skb, sizeof(struct ipv6hdr));

        seg6_lookup_nexthop(skb, NULL, 0);

        return dst_input(skb);

drop:
        kfree_skb(skb);
        return err;
}

/* encapsulate within an outer IPv6 header and a specified SRH */
static int input_action_end_b6_encap(struct sk_buff *skb,
                                     struct seg6_local_lwt *slwt)
{
        struct ipv6_sr_hdr *srh;
        int err = -EINVAL;

        srh = get_and_validate_srh(skb);
        if (!srh)
                goto drop;

        advance_nextseg(srh, &ipv6_hdr(skb)->daddr);

        skb_reset_inner_headers(skb);
        skb->encapsulation = 1;

        err = seg6_do_srh_encap(skb, slwt->srh, IPPROTO_IPV6);
        if (err)
                goto drop;

        skb_set_transport_header(skb, sizeof(struct ipv6hdr));

        seg6_lookup_nexthop(skb, NULL, 0);

        return dst_input(skb);

drop:
        kfree_skb(skb);
        return err;
}

DEFINE_PER_CPU(struct seg6_bpf_srh_state, seg6_bpf_srh_states) = {
        .bh_lock        = INIT_LOCAL_LOCK(bh_lock),
};

bool seg6_bpf_has_valid_srh(struct sk_buff *skb)
{
        struct seg6_bpf_srh_state *srh_state =
                this_cpu_ptr(&seg6_bpf_srh_states);
        struct ipv6_sr_hdr *srh = srh_state->srh;

        lockdep_assert_held(&srh_state->bh_lock);
        if (unlikely(srh == NULL))
                return false;

        if (unlikely(!srh_state->valid)) {
                if ((srh_state->hdrlen & 7) != 0)
                        return false;

                srh->hdrlen = (u8)(srh_state->hdrlen >> 3);
                if (!seg6_validate_srh(srh, (srh->hdrlen + 1) << 3, true))
                        return false;

                srh_state->valid = true;
        }

        return true;
}

static int input_action_end_bpf(struct sk_buff *skb,
                                struct seg6_local_lwt *slwt)
{
        struct seg6_bpf_srh_state *srh_state;
        struct ipv6_sr_hdr *srh;
        int ret;

        srh = get_and_validate_srh(skb);
        if (!srh) {
                kfree_skb(skb);
                return -EINVAL;
        }
        advance_nextseg(srh, &ipv6_hdr(skb)->daddr);

        /* The access to the per-CPU buffer srh_state is protected by running
         * always in softirq context (with disabled BH). On PREEMPT_RT the
         * required locking is provided by the following local_lock_nested_bh()
         * statement. It is also accessed by the bpf_lwt_seg6_* helpers via
         * bpf_prog_run_save_cb().
         */
        local_lock_nested_bh(&seg6_bpf_srh_states.bh_lock);
        srh_state = this_cpu_ptr(&seg6_bpf_srh_states);
        srh_state->srh = srh;
        srh_state->hdrlen = srh->hdrlen << 3;
        srh_state->valid = true;

        rcu_read_lock();
        bpf_compute_data_pointers(skb);
        ret = bpf_prog_run_save_cb(slwt->bpf.prog, skb);
        rcu_read_unlock();

        switch (ret) {
        case BPF_OK:
        case BPF_REDIRECT:
                break;
        case BPF_DROP:
                goto drop;
        default:
                pr_warn_once("bpf-seg6local: Illegal return value %u\n", ret);
                goto drop;
        }

        if (srh_state->srh && !seg6_bpf_has_valid_srh(skb))
                goto drop;
        local_unlock_nested_bh(&seg6_bpf_srh_states.bh_lock);

        if (ret != BPF_REDIRECT)
                seg6_lookup_nexthop(skb, NULL, 0);

        return dst_input(skb);

drop:
        local_unlock_nested_bh(&seg6_bpf_srh_states.bh_lock);
        kfree_skb(skb);
        return -EINVAL;
}

static struct seg6_action_desc seg6_action_table[] = {
        {
                .action         = SEG6_LOCAL_ACTION_END,
                .attrs          = 0,
                .optattrs       = SEG6_F_LOCAL_COUNTERS |
                                  SEG6_F_LOCAL_FLAVORS,
                .input          = input_action_end,
        },
        {
                .action         = SEG6_LOCAL_ACTION_END_X,
                .attrs          = SEG6_F_ATTR(SEG6_LOCAL_NH6),
                .optattrs       = SEG6_F_LOCAL_COUNTERS |
                                  SEG6_F_LOCAL_FLAVORS |
                                  SEG6_F_ATTR(SEG6_LOCAL_OIF),
                .input          = input_action_end_x,
        },
        {
                .action         = SEG6_LOCAL_ACTION_END_T,
                .attrs          = SEG6_F_ATTR(SEG6_LOCAL_TABLE),
                .optattrs       = SEG6_F_LOCAL_COUNTERS,
                .input          = input_action_end_t,
        },
        {
                .action         = SEG6_LOCAL_ACTION_END_DX2,
                .attrs          = SEG6_F_ATTR(SEG6_LOCAL_OIF),
                .optattrs       = SEG6_F_LOCAL_COUNTERS,
                .input          = input_action_end_dx2,
        },
        {
                .action         = SEG6_LOCAL_ACTION_END_DX6,
                .attrs          = SEG6_F_ATTR(SEG6_LOCAL_NH6),
                .optattrs       = SEG6_F_LOCAL_COUNTERS,
                .input          = input_action_end_dx6,
        },
        {
                .action         = SEG6_LOCAL_ACTION_END_DX4,
                .attrs          = SEG6_F_ATTR(SEG6_LOCAL_NH4),
                .optattrs       = SEG6_F_LOCAL_COUNTERS,
                .input          = input_action_end_dx4,
        },
        {
                .action         = SEG6_LOCAL_ACTION_END_DT4,
                .attrs          = SEG6_F_ATTR(SEG6_LOCAL_VRFTABLE),
                .optattrs       = SEG6_F_LOCAL_COUNTERS,
#ifdef CONFIG_NET_L3_MASTER_DEV
                .input          = input_action_end_dt4,
                .slwt_ops       = {
                                        .build_state = seg6_end_dt4_build,
                                  },
#endif
        },
        {
                .action         = SEG6_LOCAL_ACTION_END_DT6,
#ifdef CONFIG_NET_L3_MASTER_DEV
                .attrs          = 0,
                .optattrs       = SEG6_F_LOCAL_COUNTERS         |
                                  SEG6_F_ATTR(SEG6_LOCAL_TABLE) |
                                  SEG6_F_ATTR(SEG6_LOCAL_VRFTABLE),
                .slwt_ops       = {
                                        .build_state = seg6_end_dt6_build,
                                  },
#else
                .attrs          = SEG6_F_ATTR(SEG6_LOCAL_TABLE),
                .optattrs       = SEG6_F_LOCAL_COUNTERS,
#endif
                .input          = input_action_end_dt6,
        },
        {
                .action         = SEG6_LOCAL_ACTION_END_DT46,
                .attrs          = SEG6_F_ATTR(SEG6_LOCAL_VRFTABLE),
                .optattrs       = SEG6_F_LOCAL_COUNTERS,
#ifdef CONFIG_NET_L3_MASTER_DEV
                .input          = input_action_end_dt46,
                .slwt_ops       = {
                                        .build_state = seg6_end_dt46_build,
                                  },
#endif
        },
        {
                .action         = SEG6_LOCAL_ACTION_END_B6,
                .attrs          = SEG6_F_ATTR(SEG6_LOCAL_SRH),
                .optattrs       = SEG6_F_LOCAL_COUNTERS,
                .input          = input_action_end_b6,
        },
        {
                .action         = SEG6_LOCAL_ACTION_END_B6_ENCAP,
                .attrs          = SEG6_F_ATTR(SEG6_LOCAL_SRH),
                .optattrs       = SEG6_F_LOCAL_COUNTERS,
                .input          = input_action_end_b6_encap,
                .static_headroom        = sizeof(struct ipv6hdr),
        },
        {
                .action         = SEG6_LOCAL_ACTION_END_BPF,
                .attrs          = SEG6_F_ATTR(SEG6_LOCAL_BPF),
                .optattrs       = SEG6_F_LOCAL_COUNTERS,
                .input          = input_action_end_bpf,
        },

};

static struct seg6_action_desc *__get_action_desc(int action)
{
        struct seg6_action_desc *desc;
        int i, count;

        count = ARRAY_SIZE(seg6_action_table);
        for (i = 0; i < count; i++) {
                desc = &seg6_action_table[i];
                if (desc->action == action)
                        return desc;
        }

        return NULL;
}

static bool seg6_lwtunnel_counters_enabled(struct seg6_local_lwt *slwt)
{
        return slwt->parsed_optattrs & SEG6_F_LOCAL_COUNTERS;
}

static void seg6_local_update_counters(struct seg6_local_lwt *slwt,
                                       unsigned int len, int err)
{
        struct pcpu_seg6_local_counters *pcounters;

        pcounters = this_cpu_ptr(slwt->pcpu_counters);
        u64_stats_update_begin(&pcounters->syncp);

        if (likely(!err)) {
                u64_stats_inc(&pcounters->packets);
                u64_stats_add(&pcounters->bytes, len);
        } else {
                u64_stats_inc(&pcounters->errors);
        }

        u64_stats_update_end(&pcounters->syncp);
}

static int seg6_local_input_core(struct net *net, struct sock *sk,
                                 struct sk_buff *skb)
{
        struct dst_entry *orig_dst = skb_dst(skb);
        struct seg6_action_desc *desc;
        struct seg6_local_lwt *slwt;
        unsigned int len = skb->len;
        int rc;

        slwt = seg6_local_lwtunnel(orig_dst->lwtstate);
        desc = slwt->desc;

        rc = desc->input(skb, slwt);

        if (!seg6_lwtunnel_counters_enabled(slwt))
                return rc;

        seg6_local_update_counters(slwt, len, rc);

        return rc;
}

static int seg6_local_input(struct sk_buff *skb)
{
        if (skb->protocol != htons(ETH_P_IPV6)) {
                kfree_skb(skb);
                return -EINVAL;
        }

        if (static_branch_unlikely(&nf_hooks_lwtunnel_enabled))
                return NF_HOOK(NFPROTO_IPV6, NF_INET_LOCAL_IN,
                               dev_net(skb->dev), NULL, skb, skb->dev, NULL,
                               seg6_local_input_core);

        return seg6_local_input_core(dev_net(skb->dev), NULL, skb);
}

static const struct nla_policy seg6_local_policy[SEG6_LOCAL_MAX + 1] = {
        [SEG6_LOCAL_ACTION]     = { .type = NLA_U32 },
        [SEG6_LOCAL_SRH]        = { .type = NLA_BINARY },
        [SEG6_LOCAL_TABLE]      = { .type = NLA_U32 },
        [SEG6_LOCAL_VRFTABLE]   = { .type = NLA_U32 },
        [SEG6_LOCAL_NH4]        = NLA_POLICY_EXACT_LEN(sizeof(struct in_addr)),
        [SEG6_LOCAL_NH6]        = NLA_POLICY_EXACT_LEN(sizeof(struct in6_addr)),
        [SEG6_LOCAL_IIF]        = { .type = NLA_U32 },
        [SEG6_LOCAL_OIF]        = { .type = NLA_U32 },
        [SEG6_LOCAL_BPF]        = { .type = NLA_NESTED },
        [SEG6_LOCAL_COUNTERS]   = { .type = NLA_NESTED },
        [SEG6_LOCAL_FLAVORS]    = { .type = NLA_NESTED },
};

static int parse_nla_srh(struct nlattr **attrs, struct seg6_local_lwt *slwt,
                         struct netlink_ext_ack *extack)
{
        struct ipv6_sr_hdr *srh;
        int len;

        srh = nla_data(attrs[SEG6_LOCAL_SRH]);
        len = nla_len(attrs[SEG6_LOCAL_SRH]);

        /* SRH must contain at least one segment */
        if (len < sizeof(*srh) + sizeof(struct in6_addr))
                return -EINVAL;

        if (!seg6_validate_srh(srh, len, false))
                return -EINVAL;

        slwt->srh = kmemdup(srh, len, GFP_KERNEL);
        if (!slwt->srh)
                return -ENOMEM;

        slwt->headroom += len;

        return 0;
}

static int put_nla_srh(struct sk_buff *skb, struct seg6_local_lwt *slwt)
{
        struct ipv6_sr_hdr *srh;
        struct nlattr *nla;
        int len;

        srh = slwt->srh;
        len = (srh->hdrlen + 1) << 3;

        nla = nla_reserve(skb, SEG6_LOCAL_SRH, len);
        if (!nla)
                return -EMSGSIZE;

        memcpy(nla_data(nla), srh, len);

        return 0;
}

static int cmp_nla_srh(struct seg6_local_lwt *a, struct seg6_local_lwt *b)
{
        int len = (a->srh->hdrlen + 1) << 3;

        if (len != ((b->srh->hdrlen + 1) << 3))
                return 1;

        return memcmp(a->srh, b->srh, len);
}

static void destroy_attr_srh(struct seg6_local_lwt *slwt)
{
        kfree(slwt->srh);
}

static int parse_nla_table(struct nlattr **attrs, struct seg6_local_lwt *slwt,
                           struct netlink_ext_ack *extack)
{
        slwt->table = nla_get_u32(attrs[SEG6_LOCAL_TABLE]);

        return 0;
}

static int put_nla_table(struct sk_buff *skb, struct seg6_local_lwt *slwt)
{
        if (nla_put_u32(skb, SEG6_LOCAL_TABLE, slwt->table))
                return -EMSGSIZE;

        return 0;
}

static int cmp_nla_table(struct seg6_local_lwt *a, struct seg6_local_lwt *b)
{
        if (a->table != b->table)
                return 1;

        return 0;
}

static struct
seg6_end_dt_info *seg6_possible_end_dt_info(struct seg6_local_lwt *slwt)
{
#ifdef CONFIG_NET_L3_MASTER_DEV
        return &slwt->dt_info;
#else
        return ERR_PTR(-EOPNOTSUPP);
#endif
}

static int parse_nla_vrftable(struct nlattr **attrs,
                              struct seg6_local_lwt *slwt,
                              struct netlink_ext_ack *extack)
{
        struct seg6_end_dt_info *info = seg6_possible_end_dt_info(slwt);

        if (IS_ERR(info))
                return PTR_ERR(info);

        info->vrf_table = nla_get_u32(attrs[SEG6_LOCAL_VRFTABLE]);

        return 0;
}

static int put_nla_vrftable(struct sk_buff *skb, struct seg6_local_lwt *slwt)
{
        struct seg6_end_dt_info *info = seg6_possible_end_dt_info(slwt);

        if (IS_ERR(info))
                return PTR_ERR(info);

        if (nla_put_u32(skb, SEG6_LOCAL_VRFTABLE, info->vrf_table))
                return -EMSGSIZE;

        return 0;
}

static int cmp_nla_vrftable(struct seg6_local_lwt *a, struct seg6_local_lwt *b)
{
        struct seg6_end_dt_info *info_a = seg6_possible_end_dt_info(a);
        struct seg6_end_dt_info *info_b = seg6_possible_end_dt_info(b);

        if (info_a->vrf_table != info_b->vrf_table)
                return 1;

        return 0;
}

static int parse_nla_nh4(struct nlattr **attrs, struct seg6_local_lwt *slwt,
                         struct netlink_ext_ack *extack)
{
        memcpy(&slwt->nh4, nla_data(attrs[SEG6_LOCAL_NH4]),
               sizeof(struct in_addr));

        return 0;
}

static int put_nla_nh4(struct sk_buff *skb, struct seg6_local_lwt *slwt)
{
        struct nlattr *nla;

        nla = nla_reserve(skb, SEG6_LOCAL_NH4, sizeof(struct in_addr));
        if (!nla)
                return -EMSGSIZE;

        memcpy(nla_data(nla), &slwt->nh4, sizeof(struct in_addr));

        return 0;
}

static int cmp_nla_nh4(struct seg6_local_lwt *a, struct seg6_local_lwt *b)
{
        return memcmp(&a->nh4, &b->nh4, sizeof(struct in_addr));
}

static int parse_nla_nh6(struct nlattr **attrs, struct seg6_local_lwt *slwt,
                         struct netlink_ext_ack *extack)
{
        memcpy(&slwt->nh6, nla_data(attrs[SEG6_LOCAL_NH6]),
               sizeof(struct in6_addr));

        return 0;
}

static int put_nla_nh6(struct sk_buff *skb, struct seg6_local_lwt *slwt)
{
        struct nlattr *nla;

        nla = nla_reserve(skb, SEG6_LOCAL_NH6, sizeof(struct in6_addr));
        if (!nla)
                return -EMSGSIZE;

        memcpy(nla_data(nla), &slwt->nh6, sizeof(struct in6_addr));

        return 0;
}

static int cmp_nla_nh6(struct seg6_local_lwt *a, struct seg6_local_lwt *b)
{
        return memcmp(&a->nh6, &b->nh6, sizeof(struct in6_addr));
}

static int parse_nla_iif(struct nlattr **attrs, struct seg6_local_lwt *slwt,
                         struct netlink_ext_ack *extack)
{
        slwt->iif = nla_get_u32(attrs[SEG6_LOCAL_IIF]);

        return 0;
}

static int put_nla_iif(struct sk_buff *skb, struct seg6_local_lwt *slwt)
{
        if (nla_put_u32(skb, SEG6_LOCAL_IIF, slwt->iif))
                return -EMSGSIZE;

        return 0;
}

static int cmp_nla_iif(struct seg6_local_lwt *a, struct seg6_local_lwt *b)
{
        if (a->iif != b->iif)
                return 1;

        return 0;
}

static int parse_nla_oif(struct nlattr **attrs, struct seg6_local_lwt *slwt,
                         struct netlink_ext_ack *extack)
{
        slwt->oif = nla_get_u32(attrs[SEG6_LOCAL_OIF]);

        return 0;
}

static int put_nla_oif(struct sk_buff *skb, struct seg6_local_lwt *slwt)
{
        if (nla_put_u32(skb, SEG6_LOCAL_OIF, slwt->oif))
                return -EMSGSIZE;

        return 0;
}

static int cmp_nla_oif(struct seg6_local_lwt *a, struct seg6_local_lwt *b)
{
        if (a->oif != b->oif)
                return 1;

        return 0;
}

#define MAX_PROG_NAME 256
static const struct nla_policy bpf_prog_policy[SEG6_LOCAL_BPF_PROG_MAX + 1] = {
        [SEG6_LOCAL_BPF_PROG]      = { .type = NLA_U32, },
        [SEG6_LOCAL_BPF_PROG_NAME] = { .type = NLA_NUL_STRING,
                                       .len = MAX_PROG_NAME },
};

static int parse_nla_bpf(struct nlattr **attrs, struct seg6_local_lwt *slwt,
                         struct netlink_ext_ack *extack)
{
        struct nlattr *tb[SEG6_LOCAL_BPF_PROG_MAX + 1];
        struct bpf_prog *p;
        int ret;
        u32 fd;

        ret = nla_parse_nested_deprecated(tb, SEG6_LOCAL_BPF_PROG_MAX,
                                          attrs[SEG6_LOCAL_BPF],
                                          bpf_prog_policy, NULL);
        if (ret < 0)
                return ret;

        if (!tb[SEG6_LOCAL_BPF_PROG] || !tb[SEG6_LOCAL_BPF_PROG_NAME])
                return -EINVAL;

        slwt->bpf.name = nla_memdup(tb[SEG6_LOCAL_BPF_PROG_NAME], GFP_KERNEL);
        if (!slwt->bpf.name)
                return -ENOMEM;

        fd = nla_get_u32(tb[SEG6_LOCAL_BPF_PROG]);
        p = bpf_prog_get_type(fd, BPF_PROG_TYPE_LWT_SEG6LOCAL);
        if (IS_ERR(p)) {
                kfree(slwt->bpf.name);
                return PTR_ERR(p);
        }

        slwt->bpf.prog = p;
        return 0;
}

static int put_nla_bpf(struct sk_buff *skb, struct seg6_local_lwt *slwt)
{
        struct nlattr *nest;

        if (!slwt->bpf.prog)
                return 0;

        nest = nla_nest_start_noflag(skb, SEG6_LOCAL_BPF);
        if (!nest)
                return -EMSGSIZE;

        if (nla_put_u32(skb, SEG6_LOCAL_BPF_PROG, slwt->bpf.prog->aux->id))
                return -EMSGSIZE;

        if (slwt->bpf.name &&
            nla_put_string(skb, SEG6_LOCAL_BPF_PROG_NAME, slwt->bpf.name))
                return -EMSGSIZE;

        return nla_nest_end(skb, nest);
}

static int cmp_nla_bpf(struct seg6_local_lwt *a, struct seg6_local_lwt *b)
{
        if (!a->bpf.name && !b->bpf.name)
                return 0;

        if (!a->bpf.name || !b->bpf.name)
                return 1;

        return strcmp(a->bpf.name, b->bpf.name);
}

static void destroy_attr_bpf(struct seg6_local_lwt *slwt)
{
        kfree(slwt->bpf.name);
        if (slwt->bpf.prog)
                bpf_prog_put(slwt->bpf.prog);
}

static const struct
nla_policy seg6_local_counters_policy[SEG6_LOCAL_CNT_MAX + 1] = {
        [SEG6_LOCAL_CNT_PACKETS]        = { .type = NLA_U64 },
        [SEG6_LOCAL_CNT_BYTES]          = { .type = NLA_U64 },
        [SEG6_LOCAL_CNT_ERRORS]         = { .type = NLA_U64 },
};

static int parse_nla_counters(struct nlattr **attrs,
                              struct seg6_local_lwt *slwt,
                              struct netlink_ext_ack *extack)
{
        struct pcpu_seg6_local_counters __percpu *pcounters;
        struct nlattr *tb[SEG6_LOCAL_CNT_MAX + 1];
        int ret;

        ret = nla_parse_nested_deprecated(tb, SEG6_LOCAL_CNT_MAX,
                                          attrs[SEG6_LOCAL_COUNTERS],
                                          seg6_local_counters_policy, NULL);
        if (ret < 0)
                return ret;

        /* basic support for SRv6 Behavior counters requires at least:
         * packets, bytes and errors.
         */
        if (!tb[SEG6_LOCAL_CNT_PACKETS] || !tb[SEG6_LOCAL_CNT_BYTES] ||
            !tb[SEG6_LOCAL_CNT_ERRORS])
                return -EINVAL;

        /* counters are always zero initialized */
        pcounters = seg6_local_alloc_pcpu_counters(GFP_KERNEL);
        if (!pcounters)
                return -ENOMEM;

        slwt->pcpu_counters = pcounters;

        return 0;
}

static int seg6_local_fill_nla_counters(struct sk_buff *skb,
                                        struct seg6_local_counters *counters)
{
        if (nla_put_u64_64bit(skb, SEG6_LOCAL_CNT_PACKETS, counters->packets,
                              SEG6_LOCAL_CNT_PAD))
                return -EMSGSIZE;

        if (nla_put_u64_64bit(skb, SEG6_LOCAL_CNT_BYTES, counters->bytes,
                              SEG6_LOCAL_CNT_PAD))
                return -EMSGSIZE;

        if (nla_put_u64_64bit(skb, SEG6_LOCAL_CNT_ERRORS, counters->errors,
                              SEG6_LOCAL_CNT_PAD))
                return -EMSGSIZE;

        return 0;
}

static int put_nla_counters(struct sk_buff *skb, struct seg6_local_lwt *slwt)
{
        struct seg6_local_counters counters = { 0, 0, 0 };
        struct nlattr *nest;
        int rc, i;

        nest = nla_nest_start(skb, SEG6_LOCAL_COUNTERS);
        if (!nest)
                return -EMSGSIZE;

        for_each_possible_cpu(i) {
                struct pcpu_seg6_local_counters *pcounters;
                u64 packets, bytes, errors;
                unsigned int start;

                pcounters = per_cpu_ptr(slwt->pcpu_counters, i);
                do {
                        start = u64_stats_fetch_begin(&pcounters->syncp);

                        packets = u64_stats_read(&pcounters->packets);
                        bytes = u64_stats_read(&pcounters->bytes);
                        errors = u64_stats_read(&pcounters->errors);

                } while (u64_stats_fetch_retry(&pcounters->syncp, start));

                counters.packets += packets;
                counters.bytes += bytes;
                counters.errors += errors;
        }

        rc = seg6_local_fill_nla_counters(skb, &counters);
        if (rc < 0) {
                nla_nest_cancel(skb, nest);
                return rc;
        }

        return nla_nest_end(skb, nest);
}

static int cmp_nla_counters(struct seg6_local_lwt *a, struct seg6_local_lwt *b)
{
        /* a and b are equal if both have pcpu_counters set or not */
        return (!!((unsigned long)a->pcpu_counters)) ^
                (!!((unsigned long)b->pcpu_counters));
}

static void destroy_attr_counters(struct seg6_local_lwt *slwt)
{
        free_percpu(slwt->pcpu_counters);
}

static const
struct nla_policy seg6_local_flavors_policy[SEG6_LOCAL_FLV_MAX + 1] = {
        [SEG6_LOCAL_FLV_OPERATION]      = { .type = NLA_U32 },
        [SEG6_LOCAL_FLV_LCBLOCK_BITS]   = { .type = NLA_U8 },
        [SEG6_LOCAL_FLV_LCNODE_FN_BITS] = { .type = NLA_U8 },
};

/* check whether the lengths of the Locator-Block and Locator-Node Function
 * are compatible with the dimension of a C-SID container.
 */
static int seg6_chk_next_csid_cfg(__u8 block_len, __u8 func_len)
{
        /* Locator-Block and Locator-Node Function cannot exceed 128 bits
         * (i.e. C-SID container length).
         */
        if (next_csid_chk_cntr_bits(block_len, func_len))
                return -EINVAL;

        /* Locator-Block length must be greater than zero and evenly divisible
         * by 8. There must be room for a Locator-Node Function, at least.
         */
        if (next_csid_chk_lcblock_bits(block_len))
                return -EINVAL;

        /* Locator-Node Function length must be greater than zero and evenly
         * divisible by 8. There must be room for the Locator-Block.
         */
        if (next_csid_chk_lcnode_fn_bits(func_len))
                return -EINVAL;

        return 0;
}

static int seg6_parse_nla_next_csid_cfg(struct nlattr **tb,
                                        struct seg6_flavors_info *finfo,
                                        struct netlink_ext_ack *extack)
{
        __u8 func_len = SEG6_LOCAL_LCNODE_FN_DBITS;
        __u8 block_len = SEG6_LOCAL_LCBLOCK_DBITS;
        int rc;

        if (tb[SEG6_LOCAL_FLV_LCBLOCK_BITS])
                block_len = nla_get_u8(tb[SEG6_LOCAL_FLV_LCBLOCK_BITS]);

        if (tb[SEG6_LOCAL_FLV_LCNODE_FN_BITS])
                func_len = nla_get_u8(tb[SEG6_LOCAL_FLV_LCNODE_FN_BITS]);

        rc = seg6_chk_next_csid_cfg(block_len, func_len);
        if (rc < 0) {
                NL_SET_ERR_MSG(extack,
                               "Invalid Locator Block/Node Function lengths");
                return rc;
        }

        finfo->lcblock_bits = block_len;
        finfo->lcnode_func_bits = func_len;

        return 0;
}

static int parse_nla_flavors(struct nlattr **attrs, struct seg6_local_lwt *slwt,
                             struct netlink_ext_ack *extack)
{
        struct seg6_flavors_info *finfo = &slwt->flv_info;
        struct nlattr *tb[SEG6_LOCAL_FLV_MAX + 1];
        int action = slwt->action;
        __u32 fops, supp_fops;
        int rc;

        rc = nla_parse_nested_deprecated(tb, SEG6_LOCAL_FLV_MAX,
                                         attrs[SEG6_LOCAL_FLAVORS],
                                         seg6_local_flavors_policy, NULL);
        if (rc < 0)
                return rc;

        /* this attribute MUST always be present since it represents the Flavor
         * operation(s) to be carried out.
         */
        if (!tb[SEG6_LOCAL_FLV_OPERATION])
                return -EINVAL;

        fops = nla_get_u32(tb[SEG6_LOCAL_FLV_OPERATION]);
        rc = seg6_flv_supp_ops_by_action(action, &supp_fops);
        if (rc < 0 || (fops & ~supp_fops)) {
                NL_SET_ERR_MSG(extack, "Unsupported Flavor operation(s)");
                return -EOPNOTSUPP;
        }

        finfo->flv_ops = fops;

        if (seg6_next_csid_enabled(fops)) {
                /* Locator-Block and Locator-Node Function lengths can be
                 * provided by the user space. Otherwise, default values are
                 * applied.
                 */
                rc = seg6_parse_nla_next_csid_cfg(tb, finfo, extack);
                if (rc < 0)
                        return rc;
        }

        return 0;
}

static int seg6_fill_nla_next_csid_cfg(struct sk_buff *skb,
                                       struct seg6_flavors_info *finfo)
{
        if (nla_put_u8(skb, SEG6_LOCAL_FLV_LCBLOCK_BITS, finfo->lcblock_bits))
                return -EMSGSIZE;

        if (nla_put_u8(skb, SEG6_LOCAL_FLV_LCNODE_FN_BITS,
                       finfo->lcnode_func_bits))
                return -EMSGSIZE;

        return 0;
}

static int put_nla_flavors(struct sk_buff *skb, struct seg6_local_lwt *slwt)
{
        struct seg6_flavors_info *finfo = &slwt->flv_info;
        __u32 fops = finfo->flv_ops;
        struct nlattr *nest;
        int rc;

        nest = nla_nest_start(skb, SEG6_LOCAL_FLAVORS);
        if (!nest)
                return -EMSGSIZE;

        if (nla_put_u32(skb, SEG6_LOCAL_FLV_OPERATION, fops)) {
                rc = -EMSGSIZE;
                goto err;
        }

        if (seg6_next_csid_enabled(fops)) {
                rc = seg6_fill_nla_next_csid_cfg(skb, finfo);
                if (rc < 0)
                        goto err;
        }

        return nla_nest_end(skb, nest);

err:
        nla_nest_cancel(skb, nest);
        return rc;
}

static int seg6_cmp_nla_next_csid_cfg(struct seg6_flavors_info *finfo_a,
                                      struct seg6_flavors_info *finfo_b)
{
        if (finfo_a->lcblock_bits != finfo_b->lcblock_bits)
                return 1;

        if (finfo_a->lcnode_func_bits != finfo_b->lcnode_func_bits)
                return 1;

        return 0;
}

static int cmp_nla_flavors(struct seg6_local_lwt *a, struct seg6_local_lwt *b)
{
        struct seg6_flavors_info *finfo_a = &a->flv_info;
        struct seg6_flavors_info *finfo_b = &b->flv_info;

        if (finfo_a->flv_ops != finfo_b->flv_ops)
                return 1;

        if (seg6_next_csid_enabled(finfo_a->flv_ops)) {
                if (seg6_cmp_nla_next_csid_cfg(finfo_a, finfo_b))
                        return 1;
        }

        return 0;
}

static int encap_size_flavors(struct seg6_local_lwt *slwt)
{
        struct seg6_flavors_info *finfo = &slwt->flv_info;
        int nlsize;

        nlsize = nla_total_size(0) +    /* nest SEG6_LOCAL_FLAVORS */
                 nla_total_size(4);     /* SEG6_LOCAL_FLV_OPERATION */

        if (seg6_next_csid_enabled(finfo->flv_ops))
                nlsize += nla_total_size(1) + /* SEG6_LOCAL_FLV_LCBLOCK_BITS */
                          nla_total_size(1); /* SEG6_LOCAL_FLV_LCNODE_FN_BITS */

        return nlsize;
}

struct seg6_action_param {
        int (*parse)(struct nlattr **attrs, struct seg6_local_lwt *slwt,
                     struct netlink_ext_ack *extack);
        int (*put)(struct sk_buff *skb, struct seg6_local_lwt *slwt);
        int (*cmp)(struct seg6_local_lwt *a, struct seg6_local_lwt *b);

        /* optional destroy() callback useful for releasing resources which
         * have been previously acquired in the corresponding parse()
         * function.
         */
        void (*destroy)(struct seg6_local_lwt *slwt);
};

static struct seg6_action_param seg6_action_params[SEG6_LOCAL_MAX + 1] = {
        [SEG6_LOCAL_SRH]        = { .parse = parse_nla_srh,
                                    .put = put_nla_srh,
                                    .cmp = cmp_nla_srh,
                                    .destroy = destroy_attr_srh },

        [SEG6_LOCAL_TABLE]      = { .parse = parse_nla_table,
                                    .put = put_nla_table,
                                    .cmp = cmp_nla_table },

        [SEG6_LOCAL_NH4]        = { .parse = parse_nla_nh4,
                                    .put = put_nla_nh4,
                                    .cmp = cmp_nla_nh4 },

        [SEG6_LOCAL_NH6]        = { .parse = parse_nla_nh6,
                                    .put = put_nla_nh6,
                                    .cmp = cmp_nla_nh6 },

        [SEG6_LOCAL_IIF]        = { .parse = parse_nla_iif,
                                    .put = put_nla_iif,
                                    .cmp = cmp_nla_iif },

        [SEG6_LOCAL_OIF]        = { .parse = parse_nla_oif,
                                    .put = put_nla_oif,
                                    .cmp = cmp_nla_oif },

        [SEG6_LOCAL_BPF]        = { .parse = parse_nla_bpf,
                                    .put = put_nla_bpf,
                                    .cmp = cmp_nla_bpf,
                                    .destroy = destroy_attr_bpf },

        [SEG6_LOCAL_VRFTABLE]   = { .parse = parse_nla_vrftable,
                                    .put = put_nla_vrftable,
                                    .cmp = cmp_nla_vrftable },

        [SEG6_LOCAL_COUNTERS]   = { .parse = parse_nla_counters,
                                    .put = put_nla_counters,
                                    .cmp = cmp_nla_counters,
                                    .destroy = destroy_attr_counters },

        [SEG6_LOCAL_FLAVORS]    = { .parse = parse_nla_flavors,
                                    .put = put_nla_flavors,
                                    .cmp = cmp_nla_flavors },
};

/* call the destroy() callback (if available) for each set attribute in
 * @parsed_attrs, starting from the first attribute up to the @max_parsed
 * (excluded) attribute.
 */
static void __destroy_attrs(unsigned long parsed_attrs, int max_parsed,
                            struct seg6_local_lwt *slwt)
{
        struct seg6_action_param *param;
        int i;

        /* Every required seg6local attribute is identified by an ID which is
         * encoded as a flag (i.e: 1 << ID) in the 'attrs' bitmask;
         *
         * We scan the 'parsed_attrs' bitmask, starting from the first attribute
         * up to the @max_parsed (excluded) attribute.
         * For each set attribute, we retrieve the corresponding destroy()
         * callback. If the callback is not available, then we skip to the next
         * attribute; otherwise, we call the destroy() callback.
         */
        for (i = SEG6_LOCAL_SRH; i < max_parsed; ++i) {
                if (!(parsed_attrs & SEG6_F_ATTR(i)))
                        continue;

                param = &seg6_action_params[i];

                if (param->destroy)
                        param->destroy(slwt);
        }
}

/* release all the resources that may have been acquired during parsing
 * operations.
 */
static void destroy_attrs(struct seg6_local_lwt *slwt)
{
        unsigned long attrs = slwt->desc->attrs | slwt->parsed_optattrs;

        __destroy_attrs(attrs, SEG6_LOCAL_MAX + 1, slwt);
}

static int parse_nla_optional_attrs(struct nlattr **attrs,
                                    struct seg6_local_lwt *slwt,
                                    struct netlink_ext_ack *extack)
{
        struct seg6_action_desc *desc = slwt->desc;
        unsigned long parsed_optattrs = 0;
        struct seg6_action_param *param;
        int err, i;

        for (i = SEG6_LOCAL_SRH; i < SEG6_LOCAL_MAX + 1; ++i) {
                if (!(desc->optattrs & SEG6_F_ATTR(i)) || !attrs[i])
                        continue;

                /* once here, the i-th attribute is provided by the
                 * userspace AND it is identified optional as well.
                 */
                param = &seg6_action_params[i];

                err = param->parse(attrs, slwt, extack);
                if (err < 0)
                        goto parse_optattrs_err;

                /* current attribute has been correctly parsed */
                parsed_optattrs |= SEG6_F_ATTR(i);
        }

        /* store in the tunnel state all the optional attributed successfully
         * parsed.
         */
        slwt->parsed_optattrs = parsed_optattrs;

        return 0;

parse_optattrs_err:
        __destroy_attrs(parsed_optattrs, i, slwt);

        return err;
}

/* call the custom constructor of the behavior during its initialization phase
 * and after that all its attributes have been parsed successfully.
 */
static int
seg6_local_lwtunnel_build_state(struct seg6_local_lwt *slwt, const void *cfg,
                                struct netlink_ext_ack *extack)
{
        struct seg6_action_desc *desc = slwt->desc;
        struct seg6_local_lwtunnel_ops *ops;

        ops = &desc->slwt_ops;
        if (!ops->build_state)
                return 0;

        return ops->build_state(slwt, cfg, extack);
}

/* call the custom destructor of the behavior which is invoked before the
 * tunnel is going to be destroyed.
 */
static void seg6_local_lwtunnel_destroy_state(struct seg6_local_lwt *slwt)
{
        struct seg6_action_desc *desc = slwt->desc;
        struct seg6_local_lwtunnel_ops *ops;

        ops = &desc->slwt_ops;
        if (!ops->destroy_state)
                return;

        ops->destroy_state(slwt);
}

static int parse_nla_action(struct nlattr **attrs, struct seg6_local_lwt *slwt,
                            struct netlink_ext_ack *extack)
{
        struct seg6_action_param *param;
        struct seg6_action_desc *desc;
        unsigned long invalid_attrs;
        int i, err;

        desc = __get_action_desc(slwt->action);
        if (!desc)
                return -EINVAL;

        if (!desc->input)
                return -EOPNOTSUPP;

        slwt->desc = desc;
        slwt->headroom += desc->static_headroom;

        /* Forcing the desc->optattrs *set* and the desc->attrs *set* to be
         * disjoined, this allow us to release acquired resources by optional
         * attributes and by required attributes independently from each other
         * without any interference.
         * In other terms, we are sure that we do not release some the acquired
         * resources twice.
         *
         * Note that if an attribute is configured both as required and as
         * optional, it means that the user has messed something up in the
         * seg6_action_table. Therefore, this check is required for SRv6
         * behaviors to work properly.
         */
        invalid_attrs = desc->attrs & desc->optattrs;
        if (invalid_attrs) {
                WARN_ONCE(1,
                          "An attribute cannot be both required AND optional");
                return -EINVAL;
        }

        /* parse the required attributes */
        for (i = SEG6_LOCAL_SRH; i < SEG6_LOCAL_MAX + 1; i++) {
                if (desc->attrs & SEG6_F_ATTR(i)) {
                        if (!attrs[i])
                                return -EINVAL;

                        param = &seg6_action_params[i];

                        err = param->parse(attrs, slwt, extack);
                        if (err < 0)
                                goto parse_attrs_err;
                }
        }

        /* parse the optional attributes, if any */
        err = parse_nla_optional_attrs(attrs, slwt, extack);
        if (err < 0)
                goto parse_attrs_err;

        return 0;

parse_attrs_err:
        /* release any resource that may have been acquired during the i-1
         * parse() operations.
         */
        __destroy_attrs(desc->attrs, i, slwt);

        return err;
}

static int seg6_local_build_state(struct net *net, struct nlattr *nla,
                                  unsigned int family, const void *cfg,
                                  struct lwtunnel_state **ts,
                                  struct netlink_ext_ack *extack)
{
        struct nlattr *tb[SEG6_LOCAL_MAX + 1];
        struct lwtunnel_state *newts;
        struct seg6_local_lwt *slwt;
        int err;

        if (family != AF_INET6)
                return -EINVAL;

        err = nla_parse_nested_deprecated(tb, SEG6_LOCAL_MAX, nla,
                                          seg6_local_policy, extack);

        if (err < 0)
                return err;

        if (!tb[SEG6_LOCAL_ACTION])
                return -EINVAL;

        newts = lwtunnel_state_alloc(sizeof(*slwt));
        if (!newts)
                return -ENOMEM;

        slwt = seg6_local_lwtunnel(newts);
        slwt->action = nla_get_u32(tb[SEG6_LOCAL_ACTION]);

        err = parse_nla_action(tb, slwt, extack);
        if (err < 0)
                goto out_free;

        err = seg6_local_lwtunnel_build_state(slwt, cfg, extack);
        if (err < 0)
                goto out_destroy_attrs;

        newts->type = LWTUNNEL_ENCAP_SEG6_LOCAL;
        newts->flags = LWTUNNEL_STATE_INPUT_REDIRECT;
        newts->headroom = slwt->headroom;

        *ts = newts;

        return 0;

out_destroy_attrs:
        destroy_attrs(slwt);
out_free:
        kfree(newts);
        return err;
}

static void seg6_local_destroy_state(struct lwtunnel_state *lwt)
{
        struct seg6_local_lwt *slwt = seg6_local_lwtunnel(lwt);

        seg6_local_lwtunnel_destroy_state(slwt);

        destroy_attrs(slwt);

        return;
}

static int seg6_local_fill_encap(struct sk_buff *skb,
                                 struct lwtunnel_state *lwt)
{
        struct seg6_local_lwt *slwt = seg6_local_lwtunnel(lwt);
        struct seg6_action_param *param;
        unsigned long attrs;
        int i, err;

        if (nla_put_u32(skb, SEG6_LOCAL_ACTION, slwt->action))
                return -EMSGSIZE;

        attrs = slwt->desc->attrs | slwt->parsed_optattrs;

        for (i = SEG6_LOCAL_SRH; i < SEG6_LOCAL_MAX + 1; i++) {
                if (attrs & SEG6_F_ATTR(i)) {
                        param = &seg6_action_params[i];
                        err = param->put(skb, slwt);
                        if (err < 0)
                                return err;
                }
        }

        return 0;
}

static int seg6_local_get_encap_size(struct lwtunnel_state *lwt)
{
        struct seg6_local_lwt *slwt = seg6_local_lwtunnel(lwt);
        unsigned long attrs;
        int nlsize;

        nlsize = nla_total_size(4); /* action */

        attrs = slwt->desc->attrs | slwt->parsed_optattrs;

        if (attrs & SEG6_F_ATTR(SEG6_LOCAL_SRH))
                nlsize += nla_total_size((slwt->srh->hdrlen + 1) << 3);

        if (attrs & SEG6_F_ATTR(SEG6_LOCAL_TABLE))
                nlsize += nla_total_size(4);

        if (attrs & SEG6_F_ATTR(SEG6_LOCAL_NH4))
                nlsize += nla_total_size(4);

        if (attrs & SEG6_F_ATTR(SEG6_LOCAL_NH6))
                nlsize += nla_total_size(16);

        if (attrs & SEG6_F_ATTR(SEG6_LOCAL_IIF))
                nlsize += nla_total_size(4);

        if (attrs & SEG6_F_ATTR(SEG6_LOCAL_OIF))
                nlsize += nla_total_size(4);

        if (attrs & SEG6_F_ATTR(SEG6_LOCAL_BPF))
                nlsize += nla_total_size(sizeof(struct nlattr)) +
                       nla_total_size(MAX_PROG_NAME) +
                       nla_total_size(4);

        if (attrs & SEG6_F_ATTR(SEG6_LOCAL_VRFTABLE))
                nlsize += nla_total_size(4);

        if (attrs & SEG6_F_LOCAL_COUNTERS)
                nlsize += nla_total_size(0) + /* nest SEG6_LOCAL_COUNTERS */
                          /* SEG6_LOCAL_CNT_PACKETS */
                          nla_total_size_64bit(sizeof(__u64)) +
                          /* SEG6_LOCAL_CNT_BYTES */
                          nla_total_size_64bit(sizeof(__u64)) +
                          /* SEG6_LOCAL_CNT_ERRORS */
                          nla_total_size_64bit(sizeof(__u64));

        if (attrs & SEG6_F_ATTR(SEG6_LOCAL_FLAVORS))
                nlsize += encap_size_flavors(slwt);

        return nlsize;
}

static int seg6_local_cmp_encap(struct lwtunnel_state *a,
                                struct lwtunnel_state *b)
{
        struct seg6_local_lwt *slwt_a, *slwt_b;
        struct seg6_action_param *param;
        unsigned long attrs_a, attrs_b;
        int i;

        slwt_a = seg6_local_lwtunnel(a);
        slwt_b = seg6_local_lwtunnel(b);

        if (slwt_a->action != slwt_b->action)
                return 1;

        attrs_a = slwt_a->desc->attrs | slwt_a->parsed_optattrs;
        attrs_b = slwt_b->desc->attrs | slwt_b->parsed_optattrs;

        if (attrs_a != attrs_b)
                return 1;

        for (i = SEG6_LOCAL_SRH; i < SEG6_LOCAL_MAX + 1; i++) {
                if (attrs_a & SEG6_F_ATTR(i)) {
                        param = &seg6_action_params[i];
                        if (param->cmp(slwt_a, slwt_b))
                                return 1;
                }
        }

        return 0;
}

static const struct lwtunnel_encap_ops seg6_local_ops = {
        .build_state    = seg6_local_build_state,
        .destroy_state  = seg6_local_destroy_state,
        .input          = seg6_local_input,
        .fill_encap     = seg6_local_fill_encap,
        .get_encap_size = seg6_local_get_encap_size,
        .cmp_encap      = seg6_local_cmp_encap,
        .owner          = THIS_MODULE,
};

int __init seg6_local_init(void)
{
        /* If the max total number of defined attributes is reached, then your
         * kernel build stops here.
         *
         * This check is required to avoid arithmetic overflows when processing
         * behavior attributes and the maximum number of defined attributes
         * exceeds the allowed value.
         */
        BUILD_BUG_ON(SEG6_LOCAL_MAX + 1 > BITS_PER_TYPE(unsigned long));

        /* Check whether the number of defined flavors exceeds the maximum
         * allowed value.
         */
        BUILD_BUG_ON(SEG6_LOCAL_FLV_OP_MAX + 1 > BITS_PER_TYPE(__u32));

        /* If the default NEXT-C-SID Locator-Block/Node Function lengths (in
         * bits) have been changed with invalid values, kernel build stops
         * here.
         */
        BUILD_BUG_ON(next_csid_chk_cntr_bits(SEG6_LOCAL_LCBLOCK_DBITS,
                                             SEG6_LOCAL_LCNODE_FN_DBITS));
        BUILD_BUG_ON(next_csid_chk_lcblock_bits(SEG6_LOCAL_LCBLOCK_DBITS));
        BUILD_BUG_ON(next_csid_chk_lcnode_fn_bits(SEG6_LOCAL_LCNODE_FN_DBITS));

        /* To be memory efficient, we use 'u8' to represent the different
         * actions related to RFC8986 flavors. If the kernel build stops here,
         * it means that it is not possible to correctly encode these actions
         * with the data type chosen for the action table.
         */
        BUILD_BUG_ON(SEG6_LOCAL_FLV_ACT_MAX > (typeof(flv8986_act_tbl[0]))~0U);

        return lwtunnel_encap_add_ops(&seg6_local_ops,
                                      LWTUNNEL_ENCAP_SEG6_LOCAL);
}

void seg6_local_exit(void)
{
        lwtunnel_encap_del_ops(&seg6_local_ops, LWTUNNEL_ENCAP_SEG6_LOCAL);
}