// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *      UDP over IPv6
 *      Linux INET6 implementation
 *
 *      Authors:
 *      Pedro Roque             <roque@di.fc.ul.pt>
 *
 *      Based on linux/ipv4/udp.c
 *
 *      Fixes:
 *      Hideaki YOSHIFUJI       :       sin6_scope_id support
 *      YOSHIFUJI Hideaki @USAGI and:   Support IPV6_V6ONLY socket option, which
 *      Alexey Kuznetsov                allow both IPv4 and IPv6 sockets to bind
 *                                      a single port at the same time.
 *      Kazunori MIYAZAWA @USAGI:       change process style to use ip6_append_data
 *      YOSHIFUJI Hideaki @USAGI:       convert /proc/net/udp6 to seq_file.
 */

#include <linux/bpf-cgroup.h>
#include <linux/errno.h>
#include <linux/types.h>
#include <linux/socket.h>
#include <linux/sockios.h>
#include <linux/net.h>
#include <linux/in6.h>
#include <linux/netdevice.h>
#include <linux/if_arp.h>
#include <linux/ipv6.h>
#include <linux/icmpv6.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/skbuff.h>
#include <linux/slab.h>
#include <linux/uaccess.h>
#include <linux/indirect_call_wrapper.h>
#include <trace/events/udp.h>

#include <net/addrconf.h>
#include <net/aligned_data.h>
#include <net/ndisc.h>
#include <net/protocol.h>
#include <net/transp_v6.h>
#include <net/ip6_route.h>
#include <net/raw.h>
#include <net/seg6.h>
#include <net/tcp_states.h>
#include <net/ip6_checksum.h>
#include <net/ip6_tunnel.h>
#include <net/udp_tunnel.h>
#include <net/xfrm.h>
#include <net/inet_hashtables.h>
#include <net/inet6_hashtables.h>
#include <net/busy_poll.h>
#include <net/sock_reuseport.h>
#include <net/gro.h>

#include <linux/proc_fs.h>
#include <linux/seq_file.h>
#include <trace/events/skb.h>

static void udpv6_destruct_sock(struct sock *sk)
{
        udp_destruct_common(sk);
        inet6_sock_destruct(sk);
}

static int udpv6_init_sock(struct sock *sk)
{
        int res = udp_lib_init_sock(sk);

        sk->sk_destruct = udpv6_destruct_sock;
        set_bit(SOCK_SUPPORT_ZC, &sk->sk_socket->flags);
        return res;
}

INDIRECT_CALLABLE_SCOPE
u32 udp6_ehashfn(const struct net *net,
                 const struct in6_addr *laddr,
                 const u16 lport,
                 const struct in6_addr *faddr,
                 const __be16 fport)
{
        u32 lhash, fhash;

        net_get_random_once(&udp6_ehash_secret,
                            sizeof(udp6_ehash_secret));
        net_get_random_once(&udp_ipv6_hash_secret,
                            sizeof(udp_ipv6_hash_secret));

        lhash = (__force u32)laddr->s6_addr32[3];
        fhash = __ipv6_addr_jhash(faddr, udp_ipv6_hash_secret);

        return __inet6_ehashfn(lhash, lport, fhash, fport,
                               udp6_ehash_secret + net_hash_mix(net));
}

static int udp_v6_get_port(struct sock *sk, unsigned short snum)
{
        unsigned int hash2_nulladdr =
                ipv6_portaddr_hash(sock_net(sk), &in6addr_any, snum);
        unsigned int hash2_partial =
                ipv6_portaddr_hash(sock_net(sk), &sk->sk_v6_rcv_saddr, 0);

        /* precompute partial secondary hash */
        udp_sk(sk)->udp_portaddr_hash = hash2_partial;
        return udp_lib_get_port(sk, snum, hash2_nulladdr);
}

static void udp_v6_rehash(struct sock *sk)
{
        u16 new_hash = ipv6_portaddr_hash(sock_net(sk),
                                          &sk->sk_v6_rcv_saddr,
                                          inet_sk(sk)->inet_num);
        u16 new_hash4;

        if (ipv6_addr_v4mapped(&sk->sk_v6_rcv_saddr)) {
                new_hash4 = udp_ehashfn(sock_net(sk),
                                        sk->sk_rcv_saddr, sk->sk_num,
                                        sk->sk_daddr, sk->sk_dport);
        } else {
                new_hash4 = udp6_ehashfn(sock_net(sk),
                                         &sk->sk_v6_rcv_saddr, sk->sk_num,
                                         &sk->sk_v6_daddr, sk->sk_dport);
        }

        udp_lib_rehash(sk, new_hash, new_hash4);
}

static __always_inline int
compute_score(struct sock *sk, const struct net *net,
              const struct in6_addr *saddr, __be16 sport,
              const struct in6_addr *daddr, unsigned short hnum,
              int dif, int sdif)
{
        int bound_dev_if, score;
        struct inet_sock *inet;
        bool dev_match;

        if (!net_eq(sock_net(sk), net) ||
            udp_sk(sk)->udp_port_hash != hnum ||
            sk->sk_family != PF_INET6)
                return -1;

        if (!ipv6_addr_equal(&sk->sk_v6_rcv_saddr, daddr))
                return -1;

        score = 0;
        inet = inet_sk(sk);

        if (inet->inet_dport) {
                if (inet->inet_dport != sport)
                        return -1;
                score++;
        }

        if (!ipv6_addr_any(&sk->sk_v6_daddr)) {
                if (!ipv6_addr_equal(&sk->sk_v6_daddr, saddr))
                        return -1;
                score++;
        }

        bound_dev_if = READ_ONCE(sk->sk_bound_dev_if);
        dev_match = udp_sk_bound_dev_eq(net, bound_dev_if, dif, sdif);
        if (!dev_match)
                return -1;
        if (bound_dev_if)
                score++;

        if (READ_ONCE(sk->sk_incoming_cpu) == raw_smp_processor_id())
                score++;

        return score;
}

/**
 * udp6_lib_lookup1() - Simplified lookup using primary hash (destination port)
 * @net:        Network namespace
 * @saddr:      Source address, network order
 * @sport:      Source port, network order
 * @daddr:      Destination address, network order
 * @hnum:       Destination port, host order
 * @dif:        Destination interface index
 * @sdif:       Destination bridge port index, if relevant
 * @udptable:   Set of UDP hash tables
 *
 * Simplified lookup to be used as fallback if no sockets are found due to a
 * potential race between (receive) address change, and lookup happening before
 * the rehash operation. This function ignores SO_REUSEPORT groups while scoring
 * result sockets, because if we have one, we don't need the fallback at all.
 *
 * Called under rcu_read_lock().
 *
 * Return: socket with highest matching score if any, NULL if none
 */
static struct sock *udp6_lib_lookup1(const struct net *net,
                                     const struct in6_addr *saddr, __be16 sport,
                                     const struct in6_addr *daddr,
                                     unsigned int hnum, int dif, int sdif,
                                     const struct udp_table *udptable)
{
        unsigned int slot = udp_hashfn(net, hnum, udptable->mask);
        struct udp_hslot *hslot = &udptable->hash[slot];
        struct sock *sk, *result = NULL;
        int score, badness = 0;

        sk_for_each_rcu(sk, &hslot->head) {
                score = compute_score(sk, net,
                                      saddr, sport, daddr, hnum, dif, sdif);
                if (score > badness) {
                        result = sk;
                        badness = score;
                }
        }

        return result;
}

/* called with rcu_read_lock() */
static struct sock *udp6_lib_lookup2(const struct net *net,
                const struct in6_addr *saddr, __be16 sport,
                const struct in6_addr *daddr, unsigned int hnum,
                int dif, int sdif, struct udp_hslot *hslot2,
                struct sk_buff *skb)
{
        struct sock *sk, *result;
        int score, badness;
        bool need_rescore;

        result = NULL;
        badness = -1;
        udp_portaddr_for_each_entry_rcu(sk, &hslot2->head) {
                need_rescore = false;
rescore:
                score = compute_score(need_rescore ? result : sk, net, saddr,
                                      sport, daddr, hnum, dif, sdif);
                if (score > badness) {
                        badness = score;

                        if (need_rescore)
                                continue;

                        if (sk->sk_state == TCP_ESTABLISHED) {
                                result = sk;
                                continue;
                        }

                        result = inet6_lookup_reuseport(net, sk, skb, sizeof(struct udphdr),
                                                        saddr, sport, daddr, hnum, udp6_ehashfn);
                        if (!result) {
                                result = sk;
                                continue;
                        }

                        /* Fall back to scoring if group has connections */
                        if (!reuseport_has_conns(sk))
                                return result;

                        /* Reuseport logic returned an error, keep original score. */
                        if (IS_ERR(result))
                                continue;

                        /* compute_score is too long of a function to be
                         * inlined twice here, and calling it uninlined
                         * here yields measurable overhead for some
                         * workloads. Work around it by jumping
                         * backwards to rescore 'result'.
                         */
                        need_rescore = true;
                        goto rescore;
                }
        }
        return result;
}

#if IS_ENABLED(CONFIG_BASE_SMALL)
static struct sock *udp6_lib_lookup4(const struct net *net,
                                     const struct in6_addr *saddr, __be16 sport,
                                     const struct in6_addr *daddr,
                                     unsigned int hnum, int dif, int sdif,
                                     struct udp_table *udptable)
{
        return NULL;
}

static void udp6_hash4(struct sock *sk)
{
}
#else /* !CONFIG_BASE_SMALL */
static struct sock *udp6_lib_lookup4(const struct net *net,
                                     const struct in6_addr *saddr, __be16 sport,
                                     const struct in6_addr *daddr,
                                     unsigned int hnum, int dif, int sdif,
                                     struct udp_table *udptable)
{
        const __portpair ports = INET_COMBINED_PORTS(sport, hnum);
        const struct hlist_nulls_node *node;
        struct udp_hslot *hslot4;
        unsigned int hash4, slot;
        struct udp_sock *up;
        struct sock *sk;

        hash4 = udp6_ehashfn(net, daddr, hnum, saddr, sport);
        slot = hash4 & udptable->mask;
        hslot4 = &udptable->hash4[slot];

begin:
        udp_lrpa_for_each_entry_rcu(up, node, &hslot4->nulls_head) {
                sk = (struct sock *)up;
                if (inet6_match(net, sk, saddr, daddr, ports, dif, sdif))
                        return sk;
        }

        /* if the nulls value we got at the end of this lookup is not the
         * expected one, we must restart lookup. We probably met an item that
         * was moved to another chain due to rehash.
         */
        if (get_nulls_value(node) != slot)
                goto begin;

        return NULL;
}

static void udp6_hash4(struct sock *sk)
{
        struct net *net = sock_net(sk);
        unsigned int hash;

        if (ipv6_addr_v4mapped(&sk->sk_v6_rcv_saddr)) {
                udp4_hash4(sk);
                return;
        }

        if (sk_unhashed(sk) || ipv6_addr_any(&sk->sk_v6_rcv_saddr))
                return;

        hash = udp6_ehashfn(net, &sk->sk_v6_rcv_saddr, sk->sk_num,
                            &sk->sk_v6_daddr, sk->sk_dport);

        udp_lib_hash4(sk, hash);
}
#endif /* CONFIG_BASE_SMALL */

/* rcu_read_lock() must be held */
struct sock *__udp6_lib_lookup(const struct net *net,
                               const struct in6_addr *saddr, __be16 sport,
                               const struct in6_addr *daddr, __be16 dport,
                               int dif, int sdif, struct sk_buff *skb)
{
        struct udp_table *udptable = net->ipv4.udp_table;
        unsigned short hnum = ntohs(dport);
        struct udp_hslot *hslot2;
        struct sock *result, *sk;
        unsigned int hash2;

        hash2 = ipv6_portaddr_hash(net, daddr, hnum);
        hslot2 = udp_hashslot2(udptable, hash2);

        if (udp_has_hash4(hslot2)) {
                result = udp6_lib_lookup4(net, saddr, sport, daddr, hnum,
                                          dif, sdif, udptable);
                if (result) /* udp6_lib_lookup4 return sk or NULL */
                        return result;
        }

        /* Lookup connected or non-wildcard sockets */
        result = udp6_lib_lookup2(net, saddr, sport,
                                  daddr, hnum, dif, sdif,
                                  hslot2, skb);
        if (!IS_ERR_OR_NULL(result) && result->sk_state == TCP_ESTABLISHED)
                goto done;

        /* Lookup redirect from BPF */
        if (static_branch_unlikely(&bpf_sk_lookup_enabled)) {
                sk = inet6_lookup_run_sk_lookup(net, IPPROTO_UDP, skb, sizeof(struct udphdr),
                                                saddr, sport, daddr, hnum, dif,
                                                udp6_ehashfn);
                if (sk) {
                        result = sk;
                        goto done;
                }
        }

        /* Got non-wildcard socket or error on first lookup */
        if (result)
                goto done;

        /* Lookup wildcard sockets */
        hash2 = ipv6_portaddr_hash(net, &in6addr_any, hnum);
        hslot2 = udp_hashslot2(udptable, hash2);

        result = udp6_lib_lookup2(net, saddr, sport,
                                  &in6addr_any, hnum, dif, sdif,
                                  hslot2, skb);
        if (!IS_ERR_OR_NULL(result))
                goto done;

        /* Cover address change/lookup/rehash race: see __udp4_lib_lookup() */
        result = udp6_lib_lookup1(net, saddr, sport, daddr, hnum, dif, sdif,
                                  udptable);

done:
        if (IS_ERR(result))
                return NULL;
        return result;
}
EXPORT_SYMBOL_GPL(__udp6_lib_lookup);

static struct sock *__udp6_lib_lookup_skb(struct sk_buff *skb,
                                          __be16 sport, __be16 dport)
{
        const struct ipv6hdr *iph = ipv6_hdr(skb);

        return __udp6_lib_lookup(dev_net(skb->dev), &iph->saddr, sport,
                                 &iph->daddr, dport, inet6_iif(skb),
                                 inet6_sdif(skb), skb);
}

struct sock *udp6_lib_lookup_skb(const struct sk_buff *skb,
                                 __be16 sport, __be16 dport)
{
        const u16 offset = NAPI_GRO_CB(skb)->network_offsets[skb->encapsulation];
        const struct ipv6hdr *iph = (struct ipv6hdr *)(skb->data + offset);
        int iif, sdif;

        inet6_get_iif_sdif(skb, &iif, &sdif);

        return __udp6_lib_lookup(dev_net(skb->dev), &iph->saddr, sport,
                                 &iph->daddr, dport, iif, sdif, NULL);
}

/* Must be called under rcu_read_lock().
 * Does increment socket refcount.
 */
#if IS_ENABLED(CONFIG_NF_TPROXY_IPV6) || IS_ENABLED(CONFIG_NF_SOCKET_IPV6)
struct sock *udp6_lib_lookup(const struct net *net, const struct in6_addr *saddr, __be16 sport,
                             const struct in6_addr *daddr, __be16 dport, int dif)
{
        struct sock *sk;

        sk =  __udp6_lib_lookup(net, saddr, sport, daddr, dport, dif, 0, NULL);
        if (sk && !refcount_inc_not_zero(&sk->sk_refcnt))
                sk = NULL;
        return sk;
}
EXPORT_SYMBOL_GPL(udp6_lib_lookup);
#endif

/* do not use the scratch area len for jumbogram: their length exceeds the
 * scratch area space; note that the IP6CB flags is still in the first
 * cacheline, so checking for jumbograms is cheap
 */
static int udp6_skb_len(struct sk_buff *skb)
{
        return unlikely(inet6_is_jumbogram(skb)) ? skb->len : udp_skb_len(skb);
}

/*
 *      This should be easy, if there is something there we
 *      return it, otherwise we block.
 */

INDIRECT_CALLABLE_SCOPE
int udpv6_recvmsg(struct sock *sk, struct msghdr *msg, size_t len,
                  int flags)
{
        int off, is_udp4, err, peeking = flags & MSG_PEEK;
        struct ipv6_pinfo *np = inet6_sk(sk);
        struct inet_sock *inet = inet_sk(sk);
        struct udp_mib __percpu *mib;
        bool checksum_valid = false;
        unsigned int ulen, copied;
        struct sk_buff *skb;

        if (flags & MSG_ERRQUEUE)
                return ipv6_recv_error(sk, msg, len);

        if (np->rxopt.bits.rxpmtu && READ_ONCE(np->rxpmtu))
                return ipv6_recv_rxpmtu(sk, msg, len);

try_again:
        off = sk_peek_offset(sk, flags);
        skb = __skb_recv_udp(sk, flags, &off, &err);
        if (!skb)
                return err;

        ulen = udp6_skb_len(skb);
        copied = len;
        if (copied > ulen - off)
                copied = ulen - off;
        else if (copied < ulen)
                msg->msg_flags |= MSG_TRUNC;

        is_udp4 = (skb->protocol == htons(ETH_P_IP));
        mib = __UDPX_MIB(sk, is_udp4);

        /* If checksum is needed at all, try to do it while copying the
         * data.  If the data is truncated, do it before the copy.
         */
        if (copied < ulen || peeking) {
                checksum_valid = udp_skb_csum_unnecessary(skb) ||
                                !__udp_lib_checksum_complete(skb);
                if (!checksum_valid)
                        goto csum_copy_err;
        }

        if (checksum_valid || udp_skb_csum_unnecessary(skb)) {
                if (udp_skb_is_linear(skb))
                        err = copy_linear_skb(skb, copied, off, &msg->msg_iter);
                else
                        err = skb_copy_datagram_msg(skb, off, msg, copied);
        } else {
                err = skb_copy_and_csum_datagram_msg(skb, off, msg);
                if (err == -EINVAL)
                        goto csum_copy_err;
        }
        if (unlikely(err)) {
                if (!peeking) {
                        udp_drops_inc(sk);
                        SNMP_INC_STATS(mib, UDP_MIB_INERRORS);
                }
                kfree_skb(skb);
                return err;
        }
        if (!peeking)
                SNMP_INC_STATS(mib, UDP_MIB_INDATAGRAMS);

        sock_recv_cmsgs(msg, sk, skb);

        /* Copy the address. */
        if (msg->msg_name) {
                DECLARE_SOCKADDR(struct sockaddr_in6 *, sin6, msg->msg_name);
                sin6->sin6_family = AF_INET6;
                sin6->sin6_port = udp_hdr(skb)->source;
                sin6->sin6_flowinfo = 0;

                if (is_udp4) {
                        ipv6_addr_set_v4mapped(ip_hdr(skb)->saddr,
                                               &sin6->sin6_addr);
                        sin6->sin6_scope_id = 0;
                } else {
                        sin6->sin6_addr = ipv6_hdr(skb)->saddr;
                        sin6->sin6_scope_id =
                                ipv6_iface_scope_id(&sin6->sin6_addr,
                                                    inet6_iif(skb));
                }
                msg->msg_namelen = sizeof(*sin6);

                BPF_CGROUP_RUN_PROG_UDP6_RECVMSG_LOCK(sk,
                                                      (struct sockaddr *)sin6,
                                                      &msg->msg_namelen);
        }

        if (udp_test_bit(GRO_ENABLED, sk))
                udp_cmsg_recv(msg, sk, skb);

        if (np->rxopt.all)
                ip6_datagram_recv_common_ctl(sk, msg, skb);

        if (is_udp4) {
                if (inet_cmsg_flags(inet))
                        ip_cmsg_recv_offset(msg, sk, skb,
                                            sizeof(struct udphdr), off);
        } else {
                if (np->rxopt.all)
                        ip6_datagram_recv_specific_ctl(sk, msg, skb);
        }

        err = copied;
        if (flags & MSG_TRUNC)
                err = ulen;

        skb_consume_udp(sk, skb, peeking ? -err : err);
        return err;

csum_copy_err:
        if (!__sk_queue_drop_skb(sk, &udp_sk(sk)->reader_queue, skb, flags,
                                 udp_skb_destructor)) {
                SNMP_INC_STATS(mib, UDP_MIB_CSUMERRORS);
                SNMP_INC_STATS(mib, UDP_MIB_INERRORS);
        }
        kfree_skb_reason(skb, SKB_DROP_REASON_UDP_CSUM);

        /* starting over for a new packet, but check if we need to yield */
        cond_resched();
        msg->msg_flags &= ~MSG_TRUNC;
        goto try_again;
}

DECLARE_STATIC_KEY_FALSE(udpv6_encap_needed_key);
void udpv6_encap_enable(void)
{
        static_branch_inc(&udpv6_encap_needed_key);
}
EXPORT_SYMBOL(udpv6_encap_enable);

/* Handler for tunnels with arbitrary destination ports: no socket lookup, go
 * through error handlers in encapsulations looking for a match.
 */
static int __udp6_lib_err_encap_no_sk(struct sk_buff *skb,
                                      struct inet6_skb_parm *opt,
                                      u8 type, u8 code, int offset, __be32 info)
{
        int i;

        for (i = 0; i < MAX_IPTUN_ENCAP_OPS; i++) {
                int (*handler)(struct sk_buff *skb, struct inet6_skb_parm *opt,
                               u8 type, u8 code, int offset, __be32 info);
                const struct ip6_tnl_encap_ops *encap;

                encap = rcu_dereference(ip6tun_encaps[i]);
                if (!encap)
                        continue;
                handler = encap->err_handler;
                if (handler && !handler(skb, opt, type, code, offset, info))
                        return 0;
        }

        return -ENOENT;
}

/* Try to match ICMP errors to UDP tunnels by looking up a socket without
 * reversing source and destination port: this will match tunnels that force the
 * same destination port on both endpoints (e.g. VXLAN, GENEVE). Note that
 * lwtunnels might actually break this assumption by being configured with
 * different destination ports on endpoints, in this case we won't be able to
 * trace ICMP messages back to them.
 *
 * If this doesn't match any socket, probe tunnels with arbitrary destination
 * ports (e.g. FoU, GUE): there, the receiving socket is useless, as the port
 * we've sent packets to won't necessarily match the local destination port.
 *
 * Then ask the tunnel implementation to match the error against a valid
 * association.
 *
 * Return an error if we can't find a match, the socket if we need further
 * processing, zero otherwise.
 */
static struct sock *__udp6_lib_err_encap(struct net *net,
                                         const struct ipv6hdr *hdr, int offset,
                                         struct udphdr *uh,
                                         struct sock *sk,
                                         struct sk_buff *skb,
                                         struct inet6_skb_parm *opt,
                                         u8 type, u8 code, __be32 info)
{
        int (*lookup)(struct sock *sk, struct sk_buff *skb);
        int network_offset, transport_offset;
        struct udp_sock *up;

        network_offset = skb_network_offset(skb);
        transport_offset = skb_transport_offset(skb);

        /* Network header needs to point to the outer IPv6 header inside ICMP */
        skb_reset_network_header(skb);

        /* Transport header needs to point to the UDP header */
        skb_set_transport_header(skb, offset);

        if (sk) {
                up = udp_sk(sk);

                lookup = READ_ONCE(up->encap_err_lookup);
                if (lookup && lookup(sk, skb))
                        sk = NULL;

                goto out;
        }

        sk = __udp6_lib_lookup(net, &hdr->daddr, uh->source,
                               &hdr->saddr, uh->dest,
                               inet6_iif(skb), 0, skb);
        if (sk) {
                up = udp_sk(sk);

                lookup = READ_ONCE(up->encap_err_lookup);
                if (!lookup || lookup(sk, skb))
                        sk = NULL;
        }

out:
        if (!sk) {
                sk = ERR_PTR(__udp6_lib_err_encap_no_sk(skb, opt, type, code,
                                                        offset, info));
        }

        skb_set_transport_header(skb, transport_offset);
        skb_set_network_header(skb, network_offset);

        return sk;
}

static int udpv6_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
                     u8 type, u8 code, int offset, __be32 info)
{
        const struct ipv6hdr *hdr = (const struct ipv6hdr *)skb->data;
        struct udphdr *uh = (struct udphdr *)(skb->data + offset);
        const struct in6_addr *saddr, *daddr;
        struct net *net = dev_net(skb->dev);
        struct ipv6_pinfo *np;
        bool tunnel = false;
        struct sock *sk;
        int harderr;
        int err;

        daddr = seg6_get_daddr(skb, opt) ? : &hdr->daddr;
        saddr = &hdr->saddr;
        sk = __udp6_lib_lookup(net, daddr, uh->dest, saddr, uh->source,
                               inet6_iif(skb), inet6_sdif(skb), NULL);

        if (!sk || READ_ONCE(udp_sk(sk)->encap_type)) {
                /* No socket for error: try tunnels before discarding */
                if (static_branch_unlikely(&udpv6_encap_needed_key)) {
                        sk = __udp6_lib_err_encap(net, hdr, offset, uh, sk, skb,
                                                  opt, type, code, info);
                        if (!sk)
                                return 0;
                } else
                        sk = ERR_PTR(-ENOENT);

                if (IS_ERR(sk)) {
                        __ICMP6_INC_STATS(net, __in6_dev_get(skb->dev),
                                          ICMP6_MIB_INERRORS);
                        return PTR_ERR(sk);
                }

                tunnel = true;
        }

        harderr = icmpv6_err_convert(type, code, &err);
        np = inet6_sk(sk);

        if (type == ICMPV6_PKT_TOOBIG) {
                if (!ip6_sk_accept_pmtu(sk))
                        goto out;
                ip6_sk_update_pmtu(skb, sk, info);
                if (READ_ONCE(np->pmtudisc) != IPV6_PMTUDISC_DONT)
                        harderr = 1;
        }
        if (type == NDISC_REDIRECT) {
                if (tunnel) {
                        ip6_redirect(skb, sock_net(sk), inet6_iif(skb),
                                     READ_ONCE(sk->sk_mark),
                                     sk_uid(sk));
                } else {
                        ip6_sk_redirect(skb, sk);
                }
                goto out;
        }

        /* Tunnels don't have an application socket: don't pass errors back */
        if (tunnel) {
                if (udp_sk(sk)->encap_err_rcv)
                        udp_sk(sk)->encap_err_rcv(sk, skb, err, uh->dest,
                                                  ntohl(info), (u8 *)(uh+1));
                goto out;
        }

        if (!inet6_test_bit(RECVERR6, sk)) {
                if (!harderr || sk->sk_state != TCP_ESTABLISHED)
                        goto out;
        } else {
                ipv6_icmp_error(sk, skb, err, uh->dest, ntohl(info), (u8 *)(uh+1));
        }

        sk->sk_err = err;
        sk_error_report(sk);
out:
        return 0;
}

static int __udpv6_queue_rcv_skb(struct sock *sk, struct sk_buff *skb)
{
        int rc;

        if (!ipv6_addr_any(&sk->sk_v6_daddr)) {
                sock_rps_save_rxhash(sk, skb);
                sk_mark_napi_id(sk, skb);
                sk_incoming_cpu_update(sk);
        } else {
                sk_mark_napi_id_once(sk, skb);
        }

        rc = __udp_enqueue_schedule_skb(sk, skb);
        if (rc < 0) {
                enum skb_drop_reason drop_reason;
                struct net *net = sock_net(sk);

                /* Note that an ENOMEM error is charged twice */
                if (rc == -ENOMEM) {
                        UDP6_INC_STATS(net, UDP_MIB_RCVBUFERRORS);
                        drop_reason = SKB_DROP_REASON_SOCKET_RCVBUFF;
                } else {
                        UDP6_INC_STATS(net, UDP_MIB_MEMERRORS);
                        drop_reason = SKB_DROP_REASON_PROTO_MEM;
                }
                UDP6_INC_STATS(net, UDP_MIB_INERRORS);
                trace_udp_fail_queue_rcv_skb(rc, sk, skb);
                sk_skb_reason_drop(sk, skb, drop_reason);
                return -1;
        }

        return 0;
}

static int udpv6_queue_rcv_one_skb(struct sock *sk, struct sk_buff *skb)
{
        enum skb_drop_reason drop_reason = SKB_DROP_REASON_NOT_SPECIFIED;
        struct udp_sock *up = udp_sk(sk);
        struct net *net = sock_net(sk);

        if (!xfrm6_policy_check(sk, XFRM_POLICY_IN, skb)) {
                drop_reason = SKB_DROP_REASON_XFRM_POLICY;
                goto drop;
        }
        nf_reset_ct(skb);

        if (static_branch_unlikely(&udpv6_encap_needed_key) &&
            READ_ONCE(up->encap_type)) {
                int (*encap_rcv)(struct sock *sk, struct sk_buff *skb);

                /*
                 * This is an encapsulation socket so pass the skb to
                 * the socket's udp_encap_rcv() hook. Otherwise, just
                 * fall through and pass this up the UDP socket.
                 * up->encap_rcv() returns the following value:
                 * =0 if skb was successfully passed to the encap
                 *    handler or was discarded by it.
                 * >0 if skb should be passed on to UDP.
                 * <0 if skb should be resubmitted as proto -N
                 */

                /* if we're overly short, let UDP handle it */
                encap_rcv = READ_ONCE(up->encap_rcv);
                if (encap_rcv) {
                        int ret;

                        /* Verify checksum before giving to encap */
                        if (udp_lib_checksum_complete(skb))
                                goto csum_error;

                        ret = encap_rcv(sk, skb);
                        if (ret <= 0) {
                                __UDP6_INC_STATS(net, UDP_MIB_INDATAGRAMS);
                                return -ret;
                        }
                }

                /* FALLTHROUGH -- it's a UDP Packet */
        }

        prefetch(&sk->sk_rmem_alloc);
        if (rcu_access_pointer(sk->sk_filter) &&
            udp_lib_checksum_complete(skb))
                goto csum_error;

        drop_reason = sk_filter_trim_cap(sk, skb, sizeof(struct udphdr));
        if (drop_reason)
                goto drop;

        udp_csum_pull_header(skb);

        skb_dst_drop(skb);

        return __udpv6_queue_rcv_skb(sk, skb);

csum_error:
        drop_reason = SKB_DROP_REASON_UDP_CSUM;
        __UDP6_INC_STATS(net, UDP_MIB_CSUMERRORS);
drop:
        __UDP6_INC_STATS(net, UDP_MIB_INERRORS);
        udp_drops_inc(sk);
        sk_skb_reason_drop(sk, skb, drop_reason);
        return -1;
}

static int udpv6_queue_rcv_skb(struct sock *sk, struct sk_buff *skb)
{
        struct sk_buff *next, *segs;
        int ret;

        if (likely(!udp_unexpected_gso(sk, skb)))
                return udpv6_queue_rcv_one_skb(sk, skb);

        __skb_push(skb, -skb_mac_offset(skb));
        segs = udp_rcv_segment(sk, skb, false);
        skb_list_walk_safe(segs, skb, next) {
                __skb_pull(skb, skb_transport_offset(skb));

                udp_post_segment_fix_csum(skb);
                ret = udpv6_queue_rcv_one_skb(sk, skb);
                if (ret > 0)
                        ip6_protocol_deliver_rcu(dev_net(skb->dev), skb, ret,
                                                 true);
        }
        return 0;
}

static bool __udp_v6_is_mcast_sock(struct net *net, const struct sock *sk,
                                   __be16 loc_port, const struct in6_addr *loc_addr,
                                   __be16 rmt_port, const struct in6_addr *rmt_addr,
                                   int dif, int sdif, unsigned short hnum)
{
        const struct inet_sock *inet = inet_sk(sk);

        if (!net_eq(sock_net(sk), net))
                return false;

        if (udp_sk(sk)->udp_port_hash != hnum ||
            sk->sk_family != PF_INET6 ||
            (inet->inet_dport && inet->inet_dport != rmt_port) ||
            (!ipv6_addr_any(&sk->sk_v6_daddr) &&
                    !ipv6_addr_equal(&sk->sk_v6_daddr, rmt_addr)) ||
            !udp_sk_bound_dev_eq(net, READ_ONCE(sk->sk_bound_dev_if), dif, sdif) ||
            (!ipv6_addr_any(&sk->sk_v6_rcv_saddr) &&
                    !ipv6_addr_equal(&sk->sk_v6_rcv_saddr, loc_addr)))
                return false;
        if (!inet6_mc_check(sk, loc_addr, rmt_addr))
                return false;
        return true;
}

static void udp6_csum_zero_error(struct sk_buff *skb)
{
        /* RFC 2460 section 8.1 says that we SHOULD log
         * this error. Well, it is reasonable.
         */
        net_dbg_ratelimited("IPv6: udp checksum is 0 for [%pI6c]:%u->[%pI6c]:%u\n",
                            &ipv6_hdr(skb)->saddr, ntohs(udp_hdr(skb)->source),
                            &ipv6_hdr(skb)->daddr, ntohs(udp_hdr(skb)->dest));
}

/*
 * Note: called only from the BH handler context,
 * so we don't need to lock the hashes.
 */
static int __udp6_lib_mcast_deliver(struct net *net, struct sk_buff *skb,
                                    const struct in6_addr *saddr,
                                    const struct in6_addr *daddr)
{
        struct udp_table *udptable = net->ipv4.udp_table;
        const struct udphdr *uh = udp_hdr(skb);
        unsigned int hash2, hash2_any, offset;
        unsigned short hnum = ntohs(uh->dest);
        struct sock *sk, *first = NULL;
        int sdif = inet6_sdif(skb);
        int dif = inet6_iif(skb);
        struct hlist_node *node;
        struct udp_hslot *hslot;
        struct sk_buff *nskb;
        bool use_hash2;

        hash2_any = 0;
        hash2 = 0;
        hslot = udp_hashslot(udptable, net, hnum);
        use_hash2 = hslot->count > 10;
        offset = offsetof(typeof(*sk), sk_node);

        if (use_hash2) {
                hash2_any = ipv6_portaddr_hash(net, &in6addr_any, hnum) &
                            udptable->mask;
                hash2 = ipv6_portaddr_hash(net, daddr, hnum) & udptable->mask;
start_lookup:
                hslot = &udptable->hash2[hash2].hslot;
                offset = offsetof(typeof(*sk), __sk_common.skc_portaddr_node);
        }

        sk_for_each_entry_offset_rcu(sk, node, &hslot->head, offset) {
                if (!__udp_v6_is_mcast_sock(net, sk, uh->dest, daddr,
                                            uh->source, saddr, dif, sdif,
                                            hnum))
                        continue;
                /* If zero checksum and no_check is not on for
                 * the socket then skip it.
                 */
                if (!uh->check && !udp_get_no_check6_rx(sk))
                        continue;
                if (!first) {
                        first = sk;
                        continue;
                }
                nskb = skb_clone(skb, GFP_ATOMIC);
                if (unlikely(!nskb)) {
                        udp_drops_inc(sk);
                        __UDP6_INC_STATS(net, UDP_MIB_RCVBUFERRORS);
                        __UDP6_INC_STATS(net, UDP_MIB_INERRORS);
                        continue;
                }

                if (udpv6_queue_rcv_skb(sk, nskb) > 0)
                        consume_skb(nskb);
        }

        /* Also lookup *:port if we are using hash2 and haven't done so yet. */
        if (use_hash2 && hash2 != hash2_any) {
                hash2 = hash2_any;
                goto start_lookup;
        }

        if (first) {
                if (udpv6_queue_rcv_skb(first, skb) > 0)
                        consume_skb(skb);
        } else {
                kfree_skb(skb);
                __UDP6_INC_STATS(net, UDP_MIB_IGNOREDMULTI);
        }
        return 0;
}

static void udp6_sk_rx_dst_set(struct sock *sk, struct dst_entry *dst)
{
        if (udp_sk_rx_dst_set(sk, dst))
                sk->sk_rx_dst_cookie = rt6_get_cookie(dst_rt6_info(dst));
}

/* wrapper for udp_queue_rcv_skb taking care of csum conversion and
 * return code conversion for ip layer consumption
 */
static int udp6_unicast_rcv_skb(struct sock *sk, struct sk_buff *skb,
                                struct udphdr *uh)
{
        int ret;

        if (inet_get_convert_csum(sk) && uh->check)
                skb_checksum_try_convert(skb, IPPROTO_UDP, ip6_compute_pseudo);

        ret = udpv6_queue_rcv_skb(sk, skb);

        /* a return value > 0 means to resubmit the input */
        if (ret > 0)
                return ret;
        return 0;
}

static int udp6_csum_init(struct sk_buff *skb, struct udphdr *uh)
{
        int err;

        /* To support RFC 6936 (allow zero checksum in UDP/IPV6 for tunnels)
         * we accept a checksum of zero here. When we find the socket
         * for the UDP packet we'll check if that socket allows zero checksum
         * for IPv6 (set by socket option).
         *
         * Note, we are only interested in != 0 or == 0, thus the
         * force to int.
         */
        err = (__force int)skb_checksum_init_zero_check(skb, IPPROTO_UDP, uh->check,
                                                        ip6_compute_pseudo);
        if (err)
                return err;

        if (skb->ip_summed == CHECKSUM_COMPLETE && !skb->csum_valid) {
                /* If SW calculated the value, we know it's bad */
                if (skb->csum_complete_sw)
                        return 1;

                /* HW says the value is bad. Let's validate that.
                 * skb->csum is no longer the full packet checksum,
                 * so don't treat is as such.
                 */
                skb_checksum_complete_unset(skb);
        }

        return 0;
}

INDIRECT_CALLABLE_SCOPE int udpv6_rcv(struct sk_buff *skb)
{
        enum skb_drop_reason reason = SKB_DROP_REASON_NOT_SPECIFIED;
        const struct in6_addr *saddr, *daddr;
        struct net *net = dev_net(skb->dev);
        struct sock *sk = NULL;
        struct udphdr *uh;
        bool refcounted;
        u32 ulen = 0;

        if (!pskb_may_pull(skb, sizeof(struct udphdr)))
                goto discard;

        saddr = &ipv6_hdr(skb)->saddr;
        daddr = &ipv6_hdr(skb)->daddr;
        uh = udp_hdr(skb);

        ulen = ntohs(uh->len);
        if (ulen > skb->len)
                goto short_packet;

        /* Check for jumbo payload */
        if (ulen == 0)
                ulen = skb->len;

        if (ulen < sizeof(*uh))
                goto short_packet;

        if (ulen < skb->len) {
                if (pskb_trim_rcsum(skb, ulen))
                        goto short_packet;

                saddr = &ipv6_hdr(skb)->saddr;
                daddr = &ipv6_hdr(skb)->daddr;
                uh = udp_hdr(skb);
        }

        if (udp6_csum_init(skb, uh))
                goto csum_error;

        /* Check if the socket is already available, e.g. due to early demux */
        sk = inet6_steal_sock(net, skb, sizeof(struct udphdr), saddr, uh->source, daddr, uh->dest,
                              &refcounted, udp6_ehashfn);
        if (IS_ERR(sk))
                goto no_sk;

        if (sk) {
                struct dst_entry *dst = skb_dst(skb);
                int ret;

                if (unlikely(rcu_dereference(sk->sk_rx_dst) != dst))
                        udp6_sk_rx_dst_set(sk, dst);

                if (!uh->check && !udp_get_no_check6_rx(sk)) {
                        if (refcounted)
                                sock_put(sk);
                        goto report_csum_error;
                }

                ret = udp6_unicast_rcv_skb(sk, skb, uh);
                if (refcounted)
                        sock_put(sk);
                return ret;
        }

        /*
         *      Multicast receive code
         */
        if (ipv6_addr_is_multicast(daddr))
                return __udp6_lib_mcast_deliver(net, skb, saddr, daddr);

        /* Unicast */
        sk = __udp6_lib_lookup_skb(skb, uh->source, uh->dest);
        if (sk) {
                if (!uh->check && !udp_get_no_check6_rx(sk))
                        goto report_csum_error;
                return udp6_unicast_rcv_skb(sk, skb, uh);
        }
no_sk:
        reason = SKB_DROP_REASON_NO_SOCKET;

        if (!uh->check)
                goto report_csum_error;

        if (!xfrm6_policy_check(NULL, XFRM_POLICY_IN, skb))
                goto discard;
        nf_reset_ct(skb);

        if (udp_lib_checksum_complete(skb))
                goto csum_error;

        __UDP6_INC_STATS(net, UDP_MIB_NOPORTS);
        icmpv6_send(skb, ICMPV6_DEST_UNREACH, ICMPV6_PORT_UNREACH, 0);

        sk_skb_reason_drop(sk, skb, reason);
        return 0;

short_packet:
        if (reason == SKB_DROP_REASON_NOT_SPECIFIED)
                reason = SKB_DROP_REASON_PKT_TOO_SMALL;
        net_dbg_ratelimited("UDPv6: short packet: From [%pI6c]:%u %d/%d to [%pI6c]:%u\n",
                            saddr, ntohs(uh->source),
                            ulen, skb->len,
                            daddr, ntohs(uh->dest));
        goto discard;

report_csum_error:
        udp6_csum_zero_error(skb);
csum_error:
        if (reason == SKB_DROP_REASON_NOT_SPECIFIED)
                reason = SKB_DROP_REASON_UDP_CSUM;
        __UDP6_INC_STATS(net, UDP_MIB_CSUMERRORS);
discard:
        __UDP6_INC_STATS(net, UDP_MIB_INERRORS);
        sk_skb_reason_drop(sk, skb, reason);
        return 0;
}


static struct sock *__udp6_lib_demux_lookup(struct net *net,
                        __be16 loc_port, const struct in6_addr *loc_addr,
                        __be16 rmt_port, const struct in6_addr *rmt_addr,
                        int dif, int sdif)
{
        struct udp_table *udptable = net->ipv4.udp_table;
        unsigned short hnum = ntohs(loc_port);
        struct udp_hslot *hslot2;
        unsigned int hash2;
        __portpair ports;
        struct sock *sk;

        hash2 = ipv6_portaddr_hash(net, loc_addr, hnum);
        hslot2 = udp_hashslot2(udptable, hash2);
        ports = INET_COMBINED_PORTS(rmt_port, hnum);

        udp_portaddr_for_each_entry_rcu(sk, &hslot2->head) {
                if (sk->sk_state == TCP_ESTABLISHED &&
                    inet6_match(net, sk, rmt_addr, loc_addr, ports, dif, sdif))
                        return sk;
                /* Only check first socket in chain */
                break;
        }
        return NULL;
}

void udp_v6_early_demux(struct sk_buff *skb)
{
        struct net *net = dev_net(skb->dev);
        const struct udphdr *uh;
        struct sock *sk;
        struct dst_entry *dst;
        int dif = skb->dev->ifindex;
        int sdif = inet6_sdif(skb);

        if (!pskb_may_pull(skb, skb_transport_offset(skb) +
            sizeof(struct udphdr)))
                return;

        uh = udp_hdr(skb);

        if (skb->pkt_type == PACKET_HOST)
                sk = __udp6_lib_demux_lookup(net, uh->dest,
                                             &ipv6_hdr(skb)->daddr,
                                             uh->source, &ipv6_hdr(skb)->saddr,
                                             dif, sdif);
        else
                return;

        if (!sk)
                return;

        skb->sk = sk;
        DEBUG_NET_WARN_ON_ONCE(sk_is_refcounted(sk));
        skb->destructor = sock_pfree;
        dst = rcu_dereference(sk->sk_rx_dst);

        if (dst)
                dst = dst_check(dst, sk->sk_rx_dst_cookie);
        if (dst) {
                /* set noref for now.
                 * any place which wants to hold dst has to call
                 * dst_hold_safe()
                 */
                skb_dst_set_noref(skb, dst);
        }
}

/*
 * Throw away all pending data and cancel the corking. Socket is locked.
 */
static void udp_v6_flush_pending_frames(struct sock *sk)
{
        struct udp_sock *up = udp_sk(sk);

        if (up->pending == AF_INET)
                udp_flush_pending_frames(sk);
        else if (up->pending) {
                up->len = 0;
                WRITE_ONCE(up->pending, 0);
                ip6_flush_pending_frames(sk);
        }
}

static int udpv6_pre_connect(struct sock *sk, struct sockaddr_unsized *uaddr,
                             int addr_len)
{
        if (addr_len < offsetofend(struct sockaddr, sa_family))
                return -EINVAL;
        /* The following checks are replicated from __ip6_datagram_connect()
         * and intended to prevent BPF program called below from accessing
         * bytes that are out of the bound specified by user in addr_len.
         */
        if (uaddr->sa_family == AF_INET) {
                if (ipv6_only_sock(sk))
                        return -EAFNOSUPPORT;
                return udp_pre_connect(sk, uaddr, addr_len);
        }

        if (addr_len < SIN6_LEN_RFC2133)
                return -EINVAL;

        return BPF_CGROUP_RUN_PROG_INET6_CONNECT_LOCK(sk, uaddr, &addr_len);
}

static int udpv6_connect(struct sock *sk, struct sockaddr_unsized *uaddr,
                         int addr_len)
{
        int res;

        lock_sock(sk);
        res = __ip6_datagram_connect(sk, uaddr, addr_len);
        if (!res)
                udp6_hash4(sk);
        release_sock(sk);
        return res;
}

/**
 *      udp6_hwcsum_outgoing  -  handle outgoing HW checksumming
 *      @sk:    socket we are sending on
 *      @skb:   sk_buff containing the filled-in UDP header
 *              (checksum field must be zeroed out)
 *      @saddr: source address
 *      @daddr: destination address
 *      @len:   length of packet
 */
static void udp6_hwcsum_outgoing(struct sock *sk, struct sk_buff *skb,
                                 const struct in6_addr *saddr,
                                 const struct in6_addr *daddr, int len)
{
        unsigned int offset;
        struct udphdr *uh = udp_hdr(skb);
        struct sk_buff *frags = skb_shinfo(skb)->frag_list;
        __wsum csum = 0;

        if (!frags) {
                /* Only one fragment on the socket.  */
                skb->csum_start = skb_transport_header(skb) - skb->head;
                skb->csum_offset = offsetof(struct udphdr, check);
                uh->check = ~csum_ipv6_magic(saddr, daddr, len, IPPROTO_UDP, 0);
        } else {
                /*
                 * HW-checksum won't work as there are two or more
                 * fragments on the socket so that all csums of sk_buffs
                 * should be together
                 */
                offset = skb_transport_offset(skb);
                skb->csum = skb_checksum(skb, offset, skb->len - offset, 0);
                csum = skb->csum;

                skb->ip_summed = CHECKSUM_NONE;

                do {
                        csum = csum_add(csum, frags->csum);
                } while ((frags = frags->next));

                uh->check = csum_ipv6_magic(saddr, daddr, len, IPPROTO_UDP,
                                            csum);
                if (uh->check == 0)
                        uh->check = CSUM_MANGLED_0;
        }
}

/*
 *      Sending
 */

static int udp_v6_send_skb(struct sk_buff *skb, struct flowi6 *fl6,
                           struct inet_cork *cork)
{
        struct sock *sk = skb->sk;
        int offset, len, datalen;
        struct udphdr *uh;
        int err = 0;

        offset = skb_transport_offset(skb);
        len = skb->len - offset;
        datalen = len - sizeof(*uh);

        /*
         * Create a UDP header
         */
        uh = udp_hdr(skb);
        uh->source = fl6->fl6_sport;
        uh->dest = fl6->fl6_dport;
        uh->len = htons(len);
        uh->check = 0;

        if (cork->gso_size) {
                const int hlen = skb_network_header_len(skb) +
                                 sizeof(struct udphdr);

                if (hlen + min(datalen, cork->gso_size) > cork->fragsize) {
                        kfree_skb(skb);
                        return -EMSGSIZE;
                }
                if (datalen > cork->gso_size * UDP_MAX_SEGMENTS) {
                        kfree_skb(skb);
                        return -EINVAL;
                }
                if (udp_get_no_check6_tx(sk)) {
                        kfree_skb(skb);
                        return -EINVAL;
                }
                if (dst_xfrm(skb_dst(skb))) {
                        kfree_skb(skb);
                        return -EIO;
                }

                if (datalen > cork->gso_size) {
                        skb_shinfo(skb)->gso_size = cork->gso_size;
                        skb_shinfo(skb)->gso_type = SKB_GSO_UDP_L4;
                        skb_shinfo(skb)->gso_segs = DIV_ROUND_UP(datalen,
                                                                 cork->gso_size);

                        /* Don't checksum the payload, skb will get segmented */
                        goto csum_partial;
                }
        }

        if (udp_get_no_check6_tx(sk)) {   /* UDP csum disabled */
                skb->ip_summed = CHECKSUM_NONE;
                goto send;
        } else if (skb->ip_summed == CHECKSUM_PARTIAL) { /* UDP hardware csum */
csum_partial:
                udp6_hwcsum_outgoing(sk, skb, &fl6->saddr, &fl6->daddr, len);
                goto send;
        }

        /* add protocol-dependent pseudo-header */
        uh->check = csum_ipv6_magic(&fl6->saddr, &fl6->daddr,
                                    len, IPPROTO_UDP, udp_csum(skb));
        if (uh->check == 0)
                uh->check = CSUM_MANGLED_0;

send:
        err = ip6_send_skb(skb);
        if (unlikely(err)) {
                if (err == -ENOBUFS && !inet6_test_bit(RECVERR6, sk)) {
                        UDP6_INC_STATS(sock_net(sk), UDP_MIB_SNDBUFERRORS);
                        err = 0;
                }
        } else {
                UDP6_INC_STATS(sock_net(sk), UDP_MIB_OUTDATAGRAMS);
        }
        return err;
}

static int udp_v6_push_pending_frames(struct sock *sk)
{
        struct sk_buff *skb;
        struct udp_sock  *up = udp_sk(sk);
        int err = 0;

        if (up->pending == AF_INET)
                return udp_push_pending_frames(sk);

        skb = ip6_finish_skb(sk);
        if (!skb)
                goto out;

        err = udp_v6_send_skb(skb, &inet_sk(sk)->cork.fl.u.ip6,
                              &inet_sk(sk)->cork.base);
out:
        up->len = 0;
        WRITE_ONCE(up->pending, 0);
        return err;
}

int udpv6_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
{
        int corkreq = udp_test_bit(CORK, sk) || msg->msg_flags & MSG_MORE;
        DECLARE_SOCKADDR(struct sockaddr_in6 *, sin6, msg->msg_name);
        struct ipv6_txoptions *opt_to_free = NULL;
        struct in6_addr *daddr, *final_p, final;
        struct ip6_flowlabel *flowlabel = NULL;
        struct inet_sock *inet = inet_sk(sk);
        struct ipv6_pinfo *np = inet6_sk(sk);
        struct ipv6_txoptions *opt = NULL;
        struct udp_sock *up = udp_sk(sk);
        struct ipv6_txoptions opt_space;
        int addr_len = msg->msg_namelen;
        struct inet_cork_full cork;
        struct ipcm6_cookie ipc6;
        bool connected = false;
        struct dst_entry *dst;
        struct flowi6 *fl6;
        int ulen = len;
        int err;

        fl6 = &cork.fl.u.ip6;
        ipcm6_init_sk(&ipc6, sk);
        ipc6.gso_size = READ_ONCE(up->gso_size);

        /* destination address check */
        if (sin6) {
                if (addr_len < offsetof(struct sockaddr, sa_data))
                        return -EINVAL;

                switch (sin6->sin6_family) {
                case AF_INET6:
                        if (addr_len < SIN6_LEN_RFC2133)
                                return -EINVAL;
                        daddr = &sin6->sin6_addr;
                        if (ipv6_addr_any(daddr) &&
                            ipv6_addr_v4mapped(&np->saddr))
                                ipv6_addr_set_v4mapped(htonl(INADDR_LOOPBACK),
                                                       daddr);
                        break;
                case AF_INET:
                        goto do_udp_sendmsg;
                case AF_UNSPEC:
                        msg->msg_name = sin6 = NULL;
                        msg->msg_namelen = addr_len = 0;
                        daddr = NULL;
                        break;
                default:
                        return -EINVAL;
                }
        } else if (!READ_ONCE(up->pending)) {
                if (sk->sk_state != TCP_ESTABLISHED)
                        return -EDESTADDRREQ;
                daddr = &sk->sk_v6_daddr;
        } else
                daddr = NULL;

        if (daddr) {
                if (ipv6_addr_v4mapped(daddr)) {
                        struct sockaddr_in sin;
                        sin.sin_family = AF_INET;
                        sin.sin_port = sin6 ? sin6->sin6_port : inet->inet_dport;
                        sin.sin_addr.s_addr = daddr->s6_addr32[3];
                        msg->msg_name = &sin;
                        msg->msg_namelen = sizeof(sin);
do_udp_sendmsg:
                        err = ipv6_only_sock(sk) ?
                                -ENETUNREACH : udp_sendmsg(sk, msg, len);
                        msg->msg_name = sin6;
                        msg->msg_namelen = addr_len;
                        return err;
                }
        }

        /* Rough check on arithmetic overflow,
           better check is made in ip6_append_data().
           */
        if (len > INT_MAX - sizeof(struct udphdr))
                return -EMSGSIZE;

        if (READ_ONCE(up->pending)) {
                if (READ_ONCE(up->pending) == AF_INET)
                        return udp_sendmsg(sk, msg, len);
                /*
                 * There are pending frames.
                 * The socket lock must be held while it's corked.
                 */
                lock_sock(sk);
                if (likely(up->pending)) {
                        if (unlikely(up->pending != AF_INET6)) {
                                release_sock(sk);
                                return -EAFNOSUPPORT;
                        }
                        dst = NULL;
                        goto do_append_data;
                }
                release_sock(sk);
        }
        ulen += sizeof(struct udphdr);

        memset(fl6, 0, sizeof(*fl6));

        if (sin6) {
                if (sin6->sin6_port == 0)
                        return -EINVAL;

                fl6->fl6_dport = sin6->sin6_port;
                daddr = &sin6->sin6_addr;

                if (inet6_test_bit(SNDFLOW, sk)) {
                        fl6->flowlabel = sin6->sin6_flowinfo&IPV6_FLOWINFO_MASK;
                        if (fl6->flowlabel & IPV6_FLOWLABEL_MASK) {
                                flowlabel = fl6_sock_lookup(sk, fl6->flowlabel);
                                if (IS_ERR(flowlabel))
                                        return -EINVAL;
                        }
                }

                /*
                 * Otherwise it will be difficult to maintain
                 * sk->sk_dst_cache.
                 */
                if (sk->sk_state == TCP_ESTABLISHED &&
                    ipv6_addr_equal(daddr, &sk->sk_v6_daddr))
                        daddr = &sk->sk_v6_daddr;

                if (addr_len >= sizeof(struct sockaddr_in6) &&
                    sin6->sin6_scope_id &&
                    __ipv6_addr_needs_scope_id(__ipv6_addr_type(daddr)))
                        fl6->flowi6_oif = sin6->sin6_scope_id;
        } else {
                if (sk->sk_state != TCP_ESTABLISHED)
                        return -EDESTADDRREQ;

                fl6->fl6_dport = inet->inet_dport;
                daddr = &sk->sk_v6_daddr;
                fl6->flowlabel = np->flow_label;
                connected = true;
        }

        if (!fl6->flowi6_oif)
                fl6->flowi6_oif = READ_ONCE(sk->sk_bound_dev_if);

        if (!fl6->flowi6_oif)
                fl6->flowi6_oif = np->sticky_pktinfo.ipi6_ifindex;

        fl6->flowi6_uid = sk_uid(sk);

        if (msg->msg_controllen) {
                opt = &opt_space;
                memset(opt, 0, sizeof(struct ipv6_txoptions));
                opt->tot_len = sizeof(*opt);
                ipc6.opt = opt;

                err = udp_cmsg_send(sk, msg, &ipc6.gso_size);
                if (err > 0) {
                        err = ip6_datagram_send_ctl(sock_net(sk), sk, msg, fl6,
                                                    &ipc6);
                        connected = false;
                }
                if (err < 0) {
                        fl6_sock_release(flowlabel);
                        return err;
                }
                if ((fl6->flowlabel&IPV6_FLOWLABEL_MASK) && !flowlabel) {
                        flowlabel = fl6_sock_lookup(sk, fl6->flowlabel);
                        if (IS_ERR(flowlabel))
                                return -EINVAL;
                }
                if (!(opt->opt_nflen|opt->opt_flen))
                        opt = NULL;
        }
        if (!opt) {
                opt = txopt_get(np);
                opt_to_free = opt;
        }
        if (flowlabel)
                opt = fl6_merge_options(&opt_space, flowlabel, opt);
        opt = ipv6_fixup_options(&opt_space, opt);
        ipc6.opt = opt;

        fl6->flowi6_proto = IPPROTO_UDP;
        fl6->flowi6_mark = ipc6.sockc.mark;
        fl6->daddr = *daddr;
        if (ipv6_addr_any(&fl6->saddr) && !ipv6_addr_any(&np->saddr))
                fl6->saddr = np->saddr;
        fl6->fl6_sport = inet->inet_sport;

        if (cgroup_bpf_enabled(CGROUP_UDP6_SENDMSG) && !connected) {
                err = BPF_CGROUP_RUN_PROG_UDP6_SENDMSG_LOCK(sk,
                                           (struct sockaddr *)sin6,
                                           &addr_len,
                                           &fl6->saddr);
                if (err)
                        goto out_no_dst;
                if (sin6) {
                        if (ipv6_addr_v4mapped(&sin6->sin6_addr)) {
                                /* BPF program rewrote IPv6-only by IPv4-mapped
                                 * IPv6. It's currently unsupported.
                                 */
                                err = -ENOTSUPP;
                                goto out_no_dst;
                        }
                        if (sin6->sin6_port == 0) {
                                /* BPF program set invalid port. Reject it. */
                                err = -EINVAL;
                                goto out_no_dst;
                        }
                        fl6->fl6_dport = sin6->sin6_port;
                        fl6->daddr = sin6->sin6_addr;
                }
        }

        if (ipv6_addr_any(&fl6->daddr))
                fl6->daddr.s6_addr[15] = 0x1; /* :: means loopback (BSD'ism) */

        final_p = fl6_update_dst(fl6, opt, &final);
        if (final_p)
                connected = false;

        if (!fl6->flowi6_oif && ipv6_addr_is_multicast(&fl6->daddr)) {
                fl6->flowi6_oif = READ_ONCE(np->mcast_oif);
                connected = false;
        } else if (!fl6->flowi6_oif)
                fl6->flowi6_oif = READ_ONCE(np->ucast_oif);

        security_sk_classify_flow(sk, flowi6_to_flowi_common(fl6));

        fl6->flowlabel = ip6_make_flowinfo(ipc6.tclass, fl6->flowlabel);

        dst = ip6_sk_dst_lookup_flow(sk, fl6, final_p, connected);
        if (IS_ERR(dst)) {
                err = PTR_ERR(dst);
                dst = NULL;
                goto out;
        }

        if (ipc6.hlimit < 0)
                ipc6.hlimit = ip6_sk_dst_hoplimit(np, fl6, dst);

        if (msg->msg_flags&MSG_CONFIRM)
                goto do_confirm;
back_from_confirm:

        /* Lockless fast path for the non-corking case */
        if (!corkreq) {
                struct sk_buff *skb;

                skb = ip6_make_skb(sk, ip_generic_getfrag, msg, ulen,
                                   sizeof(struct udphdr), &ipc6,
                                   dst_rt6_info(dst),
                                   msg->msg_flags, &cork);
                err = PTR_ERR(skb);
                if (!IS_ERR_OR_NULL(skb))
                        err = udp_v6_send_skb(skb, fl6, &cork.base);
                /* ip6_make_skb steals dst reference */
                goto out_no_dst;
        }

        lock_sock(sk);
        if (unlikely(up->pending)) {
                /* The socket is already corked while preparing it. */
                /* ... which is an evident application bug. --ANK */
                release_sock(sk);

                net_dbg_ratelimited("udp cork app bug 2\n");
                err = -EINVAL;
                goto out;
        }

        WRITE_ONCE(up->pending, AF_INET6);

do_append_data:
        up->len += ulen;
        err = ip6_append_data(sk, ip_generic_getfrag, msg, ulen,
                              sizeof(struct udphdr), &ipc6, fl6,
                              dst_rt6_info(dst),
                              corkreq ? msg->msg_flags|MSG_MORE : msg->msg_flags);
        if (err)
                udp_v6_flush_pending_frames(sk);
        else if (!corkreq)
                err = udp_v6_push_pending_frames(sk);
        else if (unlikely(skb_queue_empty(&sk->sk_write_queue)))
                WRITE_ONCE(up->pending, 0);

        if (err > 0)
                err = inet6_test_bit(RECVERR6, sk) ? net_xmit_errno(err) : 0;
        release_sock(sk);

out:
        dst_release(dst);
out_no_dst:
        fl6_sock_release(flowlabel);
        txopt_put(opt_to_free);
        if (!err)
                return len;
        /*
         * ENOBUFS = no kernel mem, SOCK_NOSPACE = no sndbuf space.  Reporting
         * ENOBUFS might not be good (it's not tunable per se), but otherwise
         * we don't have a good statistic (IpOutDiscards but it can be too many
         * things).  We could add another new stat but at least for now that
         * seems like overkill.
         */
        if (err == -ENOBUFS || test_bit(SOCK_NOSPACE, &sk->sk_socket->flags))
                UDP6_INC_STATS(sock_net(sk), UDP_MIB_SNDBUFERRORS);

        return err;

do_confirm:
        if (msg->msg_flags & MSG_PROBE)
                dst_confirm_neigh(dst, &fl6->daddr);
        if (!(msg->msg_flags&MSG_PROBE) || len)
                goto back_from_confirm;
        err = 0;
        goto out;
}
EXPORT_SYMBOL(udpv6_sendmsg);

static void udpv6_splice_eof(struct socket *sock)
{
        struct sock *sk = sock->sk;
        struct udp_sock *up = udp_sk(sk);

        if (!READ_ONCE(up->pending) || udp_test_bit(CORK, sk))
                return;

        lock_sock(sk);
        if (up->pending && !udp_test_bit(CORK, sk))
                udp_v6_push_pending_frames(sk);
        release_sock(sk);
}

static void udpv6_destroy_sock(struct sock *sk)
{
        struct udp_sock *up = udp_sk(sk);
        lock_sock(sk);

        /* protects from races with udp_abort() */
        sock_set_flag(sk, SOCK_DEAD);
        udp_v6_flush_pending_frames(sk);
        release_sock(sk);

        if (static_branch_unlikely(&udpv6_encap_needed_key)) {
                if (up->encap_type) {
                        void (*encap_destroy)(struct sock *sk);
                        encap_destroy = READ_ONCE(up->encap_destroy);
                        if (encap_destroy)
                                encap_destroy(sk);
                }
                if (udp_test_bit(ENCAP_ENABLED, sk)) {
                        static_branch_dec(&udpv6_encap_needed_key);
                        udp_encap_disable();
                        udp_tunnel_cleanup_gro(sk);
                }
        }
}

/*
 *      Socket option code for UDP
 */
static int udpv6_setsockopt(struct sock *sk, int level, int optname,
                            sockptr_t optval, unsigned int optlen)
{
        if (level == SOL_UDP || level == SOL_SOCKET)
                return udp_lib_setsockopt(sk, level, optname,
                                          optval, optlen,
                                          udp_v6_push_pending_frames);
        return ipv6_setsockopt(sk, level, optname, optval, optlen);
}

static int udpv6_getsockopt(struct sock *sk, int level, int optname,
                            char __user *optval, int __user *optlen)
{
        if (level == SOL_UDP)
                return udp_lib_getsockopt(sk, level, optname, optval, optlen);
        return ipv6_getsockopt(sk, level, optname, optval, optlen);
}


/* ------------------------------------------------------------------------ */
#ifdef CONFIG_PROC_FS
static int udp6_seq_show(struct seq_file *seq, void *v)
{
        if (v == SEQ_START_TOKEN) {
                seq_puts(seq, IPV6_SEQ_DGRAM_HEADER);
        } else {
                int bucket = ((struct udp_iter_state *)seq->private)->bucket;
                const struct inet_sock *inet = inet_sk((const struct sock *)v);
                __u16 srcp = ntohs(inet->inet_sport);
                __u16 destp = ntohs(inet->inet_dport);
                __ip6_dgram_sock_seq_show(seq, v, srcp, destp,
                                          udp_rqueue_get(v), bucket);
        }
        return 0;
}

static const struct seq_operations udp6_seq_ops = {
        .start          = udp_seq_start,
        .next           = udp_seq_next,
        .stop           = udp_seq_stop,
        .show           = udp6_seq_show,
};

static struct udp_seq_afinfo udp6_seq_afinfo = {
        .family         = AF_INET6,
};

int __net_init udp6_proc_init(struct net *net)
{
        if (!proc_create_net_data("udp6", 0444, net->proc_net, &udp6_seq_ops,
                        sizeof(struct udp_iter_state), &udp6_seq_afinfo))
                return -ENOMEM;
        return 0;
}

void udp6_proc_exit(struct net *net)
{
        remove_proc_entry("udp6", net->proc_net);
}
#endif /* CONFIG_PROC_FS */

/* ------------------------------------------------------------------------ */

struct proto udpv6_prot = {
        .name                   = "UDPv6",
        .owner                  = THIS_MODULE,
        .close                  = udp_lib_close,
        .pre_connect            = udpv6_pre_connect,
        .connect                = udpv6_connect,
        .disconnect             = udp_disconnect,
        .ioctl                  = udp_ioctl,
        .init                   = udpv6_init_sock,
        .destroy                = udpv6_destroy_sock,
        .setsockopt             = udpv6_setsockopt,
        .getsockopt             = udpv6_getsockopt,
        .sendmsg                = udpv6_sendmsg,
        .recvmsg                = udpv6_recvmsg,
        .splice_eof             = udpv6_splice_eof,
        .release_cb             = ip6_datagram_release_cb,
        .hash                   = udp_lib_hash,
        .unhash                 = udp_lib_unhash,
        .rehash                 = udp_v6_rehash,
        .get_port               = udp_v6_get_port,
        .put_port               = udp_lib_unhash,
#ifdef CONFIG_BPF_SYSCALL
        .psock_update_sk_prot   = udp_bpf_update_proto,
#endif

        .memory_allocated       = &net_aligned_data.udp_memory_allocated,
        .per_cpu_fw_alloc       = &udp_memory_per_cpu_fw_alloc,

        .sysctl_mem             = sysctl_udp_mem,
        .sysctl_wmem_offset     = offsetof(struct net, ipv4.sysctl_udp_wmem_min),
        .sysctl_rmem_offset     = offsetof(struct net, ipv4.sysctl_udp_rmem_min),
        .obj_size               = sizeof(struct udp6_sock),
        .ipv6_pinfo_offset = offsetof(struct udp6_sock, inet6),
        .diag_destroy           = udp_abort,
};

static struct inet_protosw udpv6_protosw = {
        .type =      SOCK_DGRAM,
        .protocol =  IPPROTO_UDP,
        .prot =      &udpv6_prot,
        .ops =       &inet6_dgram_ops,
        .flags =     INET_PROTOSW_PERMANENT,
};

int __init udpv6_init(void)
{
        int ret;

        net_hotdata.udpv6_protocol = (struct inet6_protocol) {
                .handler     = udpv6_rcv,
                .err_handler = udpv6_err,
                .flags       = INET6_PROTO_NOPOLICY | INET6_PROTO_FINAL,
        };
        ret = inet6_add_protocol(&net_hotdata.udpv6_protocol, IPPROTO_UDP);
        if (ret)
                goto out;

        ret = inet6_register_protosw(&udpv6_protosw);
        if (ret)
                goto out_udpv6_protocol;
out:
        return ret;

out_udpv6_protocol:
        inet6_del_protocol(&net_hotdata.udpv6_protocol, IPPROTO_UDP);
        goto out;
}

void udpv6_exit(void)
{
        inet6_unregister_protosw(&udpv6_protosw);
        inet6_del_protocol(&net_hotdata.udpv6_protocol, IPPROTO_UDP);
}