// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *      IPV4 GSO/GRO offload support
 *      Linux INET implementation
 *
 *      TCPv4 GSO/GRO support
 */

#include <linux/indirect_call_wrapper.h>
#include <linux/skbuff.h>
#include <net/gro.h>
#include <net/gso.h>
#include <net/tcp.h>
#include <net/protocol.h>

static void tcp_gso_tstamp(struct sk_buff *skb, struct sk_buff *gso_skb,
                           unsigned int seq, unsigned int mss)
{
        u32 flags = skb_shinfo(gso_skb)->tx_flags & SKBTX_ANY_TSTAMP;
        u32 ts_seq = skb_shinfo(gso_skb)->tskey;

        while (skb) {
                if (before(ts_seq, seq + mss)) {
                        skb_shinfo(skb)->tx_flags |= flags;
                        skb_shinfo(skb)->tskey = ts_seq;
                        return;
                }

                skb = skb->next;
                seq += mss;
        }
}

static void __tcpv4_gso_segment_csum(struct sk_buff *seg,
                                     __be32 *oldip, __be32 newip,
                                     __be16 *oldport, __be16 newport)
{
        struct tcphdr *th;
        struct iphdr *iph;

        if (*oldip == newip && *oldport == newport)
                return;

        th = tcp_hdr(seg);
        iph = ip_hdr(seg);

        inet_proto_csum_replace4(&th->check, seg, *oldip, newip, true);
        inet_proto_csum_replace2(&th->check, seg, *oldport, newport, false);
        *oldport = newport;

        csum_replace4(&iph->check, *oldip, newip);
        *oldip = newip;
}

static struct sk_buff *__tcpv4_gso_segment_list_csum(struct sk_buff *segs)
{
        const struct tcphdr *th;
        const struct iphdr *iph;
        struct sk_buff *seg;
        struct tcphdr *th2;
        struct iphdr *iph2;

        seg = segs;
        th = tcp_hdr(seg);
        iph = ip_hdr(seg);
        th2 = tcp_hdr(seg->next);
        iph2 = ip_hdr(seg->next);

        if (!(*(const u32 *)&th->source ^ *(const u32 *)&th2->source) &&
            iph->daddr == iph2->daddr && iph->saddr == iph2->saddr)
                return segs;

        while ((seg = seg->next)) {
                th2 = tcp_hdr(seg);
                iph2 = ip_hdr(seg);

                __tcpv4_gso_segment_csum(seg,
                                         &iph2->saddr, iph->saddr,
                                         &th2->source, th->source);
                __tcpv4_gso_segment_csum(seg,
                                         &iph2->daddr, iph->daddr,
                                         &th2->dest, th->dest);
        }

        return segs;
}

static struct sk_buff *__tcp4_gso_segment_list(struct sk_buff *skb,
                                              netdev_features_t features)
{
        skb = skb_segment_list(skb, features, skb_mac_header_len(skb));
        if (IS_ERR(skb))
                return skb;

        return __tcpv4_gso_segment_list_csum(skb);
}

static struct sk_buff *tcp4_gso_segment(struct sk_buff *skb,
                                        netdev_features_t features)
{
        if (!(skb_shinfo(skb)->gso_type & SKB_GSO_TCPV4))
                return ERR_PTR(-EINVAL);

        if (!pskb_may_pull(skb, sizeof(struct tcphdr)))
                return ERR_PTR(-EINVAL);

        if (skb_shinfo(skb)->gso_type & SKB_GSO_FRAGLIST) {
                struct tcphdr *th = tcp_hdr(skb);

                if ((skb_pagelen(skb) - th->doff * 4 == skb_shinfo(skb)->gso_size) &&
                    !(skb_shinfo(skb)->gso_type & SKB_GSO_DODGY))
                        return __tcp4_gso_segment_list(skb, features);

                skb->ip_summed = CHECKSUM_NONE;
        }

        if (unlikely(skb->ip_summed != CHECKSUM_PARTIAL)) {
                const struct iphdr *iph = ip_hdr(skb);
                struct tcphdr *th = tcp_hdr(skb);

                /* Set up checksum pseudo header, usually expect stack to
                 * have done this already.
                 */

                th->check = 0;
                skb->ip_summed = CHECKSUM_PARTIAL;
                __tcp_v4_send_check(skb, iph->saddr, iph->daddr);
        }

        return tcp_gso_segment(skb, features);
}

struct sk_buff *tcp_gso_segment(struct sk_buff *skb,
                                netdev_features_t features)
{
        struct sk_buff *segs = ERR_PTR(-EINVAL);
        unsigned int sum_truesize = 0;
        struct tcphdr *th;
        unsigned int thlen;
        unsigned int seq;
        unsigned int oldlen;
        unsigned int mss;
        struct sk_buff *gso_skb = skb;
        __sum16 newcheck;
        bool ooo_okay, copy_destructor;
        bool ecn_cwr_mask;
        __wsum delta;

        th = tcp_hdr(skb);
        thlen = th->doff * 4;
        if (thlen < sizeof(*th))
                goto out;

        if (unlikely(skb_checksum_start(skb) != skb_transport_header(skb)))
                goto out;

        if (!pskb_may_pull(skb, thlen))
                goto out;

        oldlen = ~skb->len;
        __skb_pull(skb, thlen);

        mss = skb_shinfo(skb)->gso_size;
        if (unlikely(skb->len <= mss))
                goto out;

        if (skb_gso_ok(skb, features | NETIF_F_GSO_ROBUST)) {
                /* Packet is from an untrusted source, reset gso_segs. */

                skb_shinfo(skb)->gso_segs = DIV_ROUND_UP(skb->len, mss);

                segs = NULL;
                goto out;
        }

        copy_destructor = gso_skb->destructor == tcp_wfree;
        ooo_okay = gso_skb->ooo_okay;
        /* All segments but the first should have ooo_okay cleared */
        skb->ooo_okay = 0;

        segs = skb_segment(skb, features);
        if (IS_ERR(segs))
                goto out;

        /* Only first segment might have ooo_okay set */
        segs->ooo_okay = ooo_okay;

        /* GSO partial and frag_list segmentation only requires splitting
         * the frame into an MSS multiple and possibly a remainder, both
         * cases return a GSO skb. So update the mss now.
         */
        if (skb_is_gso(segs))
                mss *= skb_shinfo(segs)->gso_segs;

        delta = (__force __wsum)htonl(oldlen + thlen + mss);

        skb = segs;
        th = tcp_hdr(skb);
        seq = ntohl(th->seq);

        if (unlikely(skb_shinfo(gso_skb)->tx_flags & SKBTX_ANY_TSTAMP))
                tcp_gso_tstamp(segs, gso_skb, seq, mss);

        newcheck = ~csum_fold(csum_add(csum_unfold(th->check), delta));

        ecn_cwr_mask = !!(skb_shinfo(gso_skb)->gso_type & SKB_GSO_TCP_ACCECN);

        while (skb->next) {
                th->fin = th->psh = 0;
                th->check = newcheck;

                if (skb->ip_summed == CHECKSUM_PARTIAL)
                        gso_reset_checksum(skb, ~th->check);
                else
                        th->check = gso_make_checksum(skb, ~th->check);

                seq += mss;
                if (copy_destructor) {
                        skb->destructor = gso_skb->destructor;
                        skb->sk = gso_skb->sk;
                        sum_truesize += skb->truesize;
                }
                skb = skb->next;
                th = tcp_hdr(skb);

                th->seq = htonl(seq);

                th->cwr &= ecn_cwr_mask;
        }

        /* Following permits TCP Small Queues to work well with GSO :
         * The callback to TCP stack will be called at the time last frag
         * is freed at TX completion, and not right now when gso_skb
         * is freed by GSO engine
         */
        if (copy_destructor) {
                int delta;

                swap(gso_skb->sk, skb->sk);
                swap(gso_skb->destructor, skb->destructor);
                sum_truesize += skb->truesize;
                delta = sum_truesize - gso_skb->truesize;
                /* In some pathological cases, delta can be negative.
                 * We need to either use refcount_add() or refcount_sub_and_test()
                 */
                if (likely(delta >= 0))
                        refcount_add(delta, &skb->sk->sk_wmem_alloc);
                else
                        WARN_ON_ONCE(refcount_sub_and_test(-delta, &skb->sk->sk_wmem_alloc));
        }

        delta = (__force __wsum)htonl(oldlen +
                                      (skb_tail_pointer(skb) -
                                       skb_transport_header(skb)) +
                                      skb->data_len);
        th->check = ~csum_fold(csum_add(csum_unfold(th->check), delta));
        if (skb->ip_summed == CHECKSUM_PARTIAL)
                gso_reset_checksum(skb, ~th->check);
        else
                th->check = gso_make_checksum(skb, ~th->check);
out:
        return segs;
}

struct sk_buff *tcp_gro_lookup(struct list_head *head, struct tcphdr *th)
{
        struct tcphdr *th2;
        struct sk_buff *p;

        list_for_each_entry(p, head, list) {
                if (!NAPI_GRO_CB(p)->same_flow)
                        continue;

                th2 = tcp_hdr(p);
                if (*(u32 *)&th->source ^ *(u32 *)&th2->source) {
                        NAPI_GRO_CB(p)->same_flow = 0;
                        continue;
                }

                return p;
        }

        return NULL;
}

struct sk_buff *tcp_gro_receive(struct list_head *head, struct sk_buff *skb,
                                struct tcphdr *th)
{
        unsigned int thlen = th->doff * 4;
        struct sk_buff *pp = NULL;
        struct sk_buff *p;
        struct tcphdr *th2;
        unsigned int len;
        __be32 flags;
        unsigned int mss = 1;
        int flush = 1;
        int i;

        len = skb_gro_len(skb);
        flags = tcp_flag_word(th);

        p = tcp_gro_lookup(head, th);
        if (!p)
                goto out_check_final;

        th2 = tcp_hdr(p);
        flush = (__force int)((flags ^ tcp_flag_word(th2)) &
                  ~(TCP_FLAG_FIN | TCP_FLAG_PSH));
        flush |= (__force int)(th->ack_seq ^ th2->ack_seq);
        for (i = sizeof(*th); i < thlen; i += 4)
                flush |= *(u32 *)((u8 *)th + i) ^
                         *(u32 *)((u8 *)th2 + i);

        flush |= gro_receive_network_flush(th, th2, p);

        mss = skb_shinfo(p)->gso_size;

        /* If skb is a GRO packet, make sure its gso_size matches prior packet mss.
         * If it is a single frame, do not aggregate it if its length
         * is bigger than our mss.
         */
        if (unlikely(skb_is_gso(skb)))
                flush |= (mss != skb_shinfo(skb)->gso_size);
        else
                flush |= (len - 1) >= mss;

        flush |= (ntohl(th2->seq) + skb_gro_len(p)) ^ ntohl(th->seq);
        flush |= skb_cmp_decrypted(p, skb);

        if (unlikely(NAPI_GRO_CB(p)->is_flist)) {
                flush |= (__force int)(flags ^ tcp_flag_word(th2));
                flush |= skb->ip_summed != p->ip_summed;
                flush |= skb->csum_level != p->csum_level;
                flush |= NAPI_GRO_CB(p)->count >= 64;
                skb_set_network_header(skb, skb_gro_receive_network_offset(skb));

                if (flush || skb_gro_receive_list(p, skb))
                        mss = 1;

                goto out_check_final;
        }

        if (flush || skb_gro_receive(p, skb)) {
                mss = 1;
                goto out_check_final;
        }

        tcp_flag_word(th2) |= flags & (TCP_FLAG_FIN | TCP_FLAG_PSH);

out_check_final:
        /* Force a flush if last segment is smaller than mss. */
        if (unlikely(skb_is_gso(skb)))
                flush = len != NAPI_GRO_CB(skb)->count * skb_shinfo(skb)->gso_size;
        else
                flush = len < mss;

        flush |= (__force int)(flags & (TCP_FLAG_URG | TCP_FLAG_PSH |
                                        TCP_FLAG_RST | TCP_FLAG_SYN |
                                        TCP_FLAG_FIN));

        if (p && (!NAPI_GRO_CB(skb)->same_flow || flush))
                pp = p;

        NAPI_GRO_CB(skb)->flush |= (flush != 0);

        return pp;
}

void tcp_gro_complete(struct sk_buff *skb)
{
        struct tcphdr *th = tcp_hdr(skb);
        struct skb_shared_info *shinfo;

        if (skb->encapsulation)
                skb->inner_transport_header = skb->transport_header;

        skb->csum_start = (unsigned char *)th - skb->head;
        skb->csum_offset = offsetof(struct tcphdr, check);
        skb->ip_summed = CHECKSUM_PARTIAL;

        shinfo = skb_shinfo(skb);
        shinfo->gso_segs = NAPI_GRO_CB(skb)->count;

        if (th->cwr)
                shinfo->gso_type |= SKB_GSO_TCP_ACCECN;
}
EXPORT_SYMBOL(tcp_gro_complete);

static void tcp4_check_fraglist_gro(struct list_head *head, struct sk_buff *skb,
                                    struct tcphdr *th)
{
        const struct iphdr *iph;
        struct sk_buff *p;
        struct sock *sk;
        struct net *net;
        int iif, sdif;

        if (likely(!(skb->dev->features & NETIF_F_GRO_FRAGLIST)))
                return;

        p = tcp_gro_lookup(head, th);
        if (p) {
                NAPI_GRO_CB(skb)->is_flist = NAPI_GRO_CB(p)->is_flist;
                return;
        }

        inet_get_iif_sdif(skb, &iif, &sdif);
        iph = skb_gro_network_header(skb);
        net = dev_net_rcu(skb->dev);
        sk = __inet_lookup_established(net, iph->saddr, th->source,
                                       iph->daddr, ntohs(th->dest),
                                       iif, sdif);
        NAPI_GRO_CB(skb)->is_flist = !sk;
        if (sk)
                sock_gen_put(sk);
}

INDIRECT_CALLABLE_SCOPE
struct sk_buff *tcp4_gro_receive(struct list_head *head, struct sk_buff *skb)
{
        struct tcphdr *th;

        /* Don't bother verifying checksum if we're going to flush anyway. */
        if (!NAPI_GRO_CB(skb)->flush &&
            skb_gro_checksum_validate(skb, IPPROTO_TCP,
                                      inet_gro_compute_pseudo))
                goto flush;

        th = tcp_gro_pull_header(skb);
        if (!th)
                goto flush;

        tcp4_check_fraglist_gro(head, skb, th);

        return tcp_gro_receive(head, skb, th);

flush:
        NAPI_GRO_CB(skb)->flush = 1;
        return NULL;
}

INDIRECT_CALLABLE_SCOPE int tcp4_gro_complete(struct sk_buff *skb, int thoff)
{
        const u16 offset = NAPI_GRO_CB(skb)->network_offsets[skb->encapsulation];
        const struct iphdr *iph = (struct iphdr *)(skb->data + offset);
        struct tcphdr *th = tcp_hdr(skb);

        if (unlikely(NAPI_GRO_CB(skb)->is_flist)) {
                skb_shinfo(skb)->gso_type |= SKB_GSO_FRAGLIST | SKB_GSO_TCPV4;
                skb_shinfo(skb)->gso_segs = NAPI_GRO_CB(skb)->count;

                __skb_incr_checksum_unnecessary(skb);

                return 0;
        }

        th->check = ~tcp_v4_check(skb->len - thoff, iph->saddr,
                                  iph->daddr, 0);

        BUILD_BUG_ON(SKB_GSO_TCP_FIXEDID << 1 != SKB_GSO_TCP_FIXEDID_INNER);
        skb_shinfo(skb)->gso_type |= SKB_GSO_TCPV4 |
                        (NAPI_GRO_CB(skb)->ip_fixedid * SKB_GSO_TCP_FIXEDID);

        tcp_gro_complete(skb);
        return 0;
}

int __init tcpv4_offload_init(void)
{
        net_hotdata.tcpv4_offload = (struct net_offload) {
                .callbacks = {
                        .gso_segment    =       tcp4_gso_segment,
                        .gro_receive    =       tcp4_gro_receive,
                        .gro_complete   =       tcp4_gro_complete,
                },
        };
        return inet_add_offload(&net_hotdata.tcpv4_offload, IPPROTO_TCP);
}