// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *      IPV4 GSO/GRO offload support
 *      Linux INET implementation
 *
 *      UDPv4 GSO support
 */

#include <linux/skbuff.h>
#include <net/udp.h>
#include <net/protocol.h>
#include <net/inet_common.h>

static struct sk_buff *__skb_udp_tunnel_segment(struct sk_buff *skb,
        netdev_features_t features,
        struct sk_buff *(*gso_inner_segment)(struct sk_buff *skb,
                                             netdev_features_t features),
        __be16 new_protocol, bool is_ipv6)
{
        int tnl_hlen = skb_inner_mac_header(skb) - skb_transport_header(skb);
        bool remcsum, need_csum, offload_csum, gso_partial;
        struct sk_buff *segs = ERR_PTR(-EINVAL);
        struct udphdr *uh = udp_hdr(skb);
        u16 mac_offset = skb->mac_header;
        __be16 protocol = skb->protocol;
        u16 mac_len = skb->mac_len;
        int udp_offset, outer_hlen;
        __wsum partial;
        bool need_ipsec;

        if (unlikely(!pskb_may_pull(skb, tnl_hlen)))
                goto out;

        /* Adjust partial header checksum to negate old length.
         * We cannot rely on the value contained in uh->len as it is
         * possible that the actual value exceeds the boundaries of the
         * 16 bit length field due to the header being added outside of an
         * IP or IPv6 frame that was already limited to 64K - 1.
         */
        if (skb_shinfo(skb)->gso_type & SKB_GSO_PARTIAL)
                partial = (__force __wsum)uh->len;
        else
                partial = (__force __wsum)htonl(skb->len);
        partial = csum_sub(csum_unfold(uh->check), partial);

        /* setup inner skb. */
        skb->encapsulation = 0;
        SKB_GSO_CB(skb)->encap_level = 0;
        __skb_pull(skb, tnl_hlen);
        skb_reset_mac_header(skb);
        skb_set_network_header(skb, skb_inner_network_offset(skb));
        skb->mac_len = skb_inner_network_offset(skb);
        skb->protocol = new_protocol;

        need_csum = !!(skb_shinfo(skb)->gso_type & SKB_GSO_UDP_TUNNEL_CSUM);
        skb->encap_hdr_csum = need_csum;

        remcsum = !!(skb_shinfo(skb)->gso_type & SKB_GSO_TUNNEL_REMCSUM);
        skb->remcsum_offload = remcsum;

        need_ipsec = skb_dst(skb) && dst_xfrm(skb_dst(skb));
        /* Try to offload checksum if possible */
        offload_csum = !!(need_csum &&
                          !need_ipsec &&
                          (skb->dev->features &
                           (is_ipv6 ? (NETIF_F_HW_CSUM | NETIF_F_IPV6_CSUM) :
                                      (NETIF_F_HW_CSUM | NETIF_F_IP_CSUM))));

        features &= skb->dev->hw_enc_features;

        /* The only checksum offload we care about from here on out is the
         * outer one so strip the existing checksum feature flags and
         * instead set the flag based on our outer checksum offload value.
         */
        if (remcsum) {
                features &= ~NETIF_F_CSUM_MASK;
                if (!need_csum || offload_csum)
                        features |= NETIF_F_HW_CSUM;
        }

        /* segment inner packet. */
        segs = gso_inner_segment(skb, features);
        if (IS_ERR_OR_NULL(segs)) {
                skb_gso_error_unwind(skb, protocol, tnl_hlen, mac_offset,
                                     mac_len);
                goto out;
        }

        gso_partial = !!(skb_shinfo(segs)->gso_type & SKB_GSO_PARTIAL);

        outer_hlen = skb_tnl_header_len(skb);
        udp_offset = outer_hlen - tnl_hlen;
        skb = segs;
        do {
                unsigned int len;

                if (remcsum)
                        skb->ip_summed = CHECKSUM_NONE;

                /* Set up inner headers if we are offloading inner checksum */
                if (skb->ip_summed == CHECKSUM_PARTIAL) {
                        skb_reset_inner_headers(skb);
                        skb->encapsulation = 1;
                }

                skb->mac_len = mac_len;
                skb->protocol = protocol;

                __skb_push(skb, outer_hlen);
                skb_reset_mac_header(skb);
                skb_set_network_header(skb, mac_len);
                skb_set_transport_header(skb, udp_offset);
                len = skb->len - udp_offset;
                uh = udp_hdr(skb);

                /* If we are only performing partial GSO the inner header
                 * will be using a length value equal to only one MSS sized
                 * segment instead of the entire frame.
                 */
                if (gso_partial && skb_is_gso(skb)) {
                        uh->len = htons(skb_shinfo(skb)->gso_size +
                                        SKB_GSO_CB(skb)->data_offset +
                                        skb->head - (unsigned char *)uh);
                } else {
                        uh->len = htons(len);
                }

                if (!need_csum)
                        continue;

                uh->check = ~csum_fold(csum_add(partial,
                                       (__force __wsum)htonl(len)));

                if (skb->encapsulation || !offload_csum) {
                        uh->check = gso_make_checksum(skb, ~uh->check);
                        if (uh->check == 0)
                                uh->check = CSUM_MANGLED_0;
                } else {
                        skb->ip_summed = CHECKSUM_PARTIAL;
                        skb->csum_start = skb_transport_header(skb) - skb->head;
                        skb->csum_offset = offsetof(struct udphdr, check);
                }
        } while ((skb = skb->next));
out:
        return segs;
}

struct sk_buff *skb_udp_tunnel_segment(struct sk_buff *skb,
                                       netdev_features_t features,
                                       bool is_ipv6)
{
        __be16 protocol = skb->protocol;
        const struct net_offload **offloads;
        const struct net_offload *ops;
        struct sk_buff *segs = ERR_PTR(-EINVAL);
        struct sk_buff *(*gso_inner_segment)(struct sk_buff *skb,
                                             netdev_features_t features);

        rcu_read_lock();

        switch (skb->inner_protocol_type) {
        case ENCAP_TYPE_ETHER:
                protocol = skb->inner_protocol;
                gso_inner_segment = skb_mac_gso_segment;
                break;
        case ENCAP_TYPE_IPPROTO:
                offloads = is_ipv6 ? inet6_offloads : inet_offloads;
                ops = rcu_dereference(offloads[skb->inner_ipproto]);
                if (!ops || !ops->callbacks.gso_segment)
                        goto out_unlock;
                gso_inner_segment = ops->callbacks.gso_segment;
                break;
        default:
                goto out_unlock;
        }

        segs = __skb_udp_tunnel_segment(skb, features, gso_inner_segment,
                                        protocol, is_ipv6);

out_unlock:
        rcu_read_unlock();

        return segs;
}
EXPORT_SYMBOL(skb_udp_tunnel_segment);

struct sk_buff *__udp_gso_segment(struct sk_buff *gso_skb,
                                  netdev_features_t features)
{
        struct sock *sk = gso_skb->sk;
        unsigned int sum_truesize = 0;
        struct sk_buff *segs, *seg;
        struct udphdr *uh;
        unsigned int mss;
        bool copy_dtor;
        __sum16 check;
        __be16 newlen;

        mss = skb_shinfo(gso_skb)->gso_size;
        if (gso_skb->len <= sizeof(*uh) + mss)
                return ERR_PTR(-EINVAL);

        skb_pull(gso_skb, sizeof(*uh));

        /* clear destructor to avoid skb_segment assigning it to tail */
        copy_dtor = gso_skb->destructor == sock_wfree;
        if (copy_dtor)
                gso_skb->destructor = NULL;

        segs = skb_segment(gso_skb, features);
        if (IS_ERR_OR_NULL(segs)) {
                if (copy_dtor)
                        gso_skb->destructor = sock_wfree;
                return segs;
        }

        /* 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;

        seg = segs;
        uh = udp_hdr(seg);

        /* preserve TX timestamp flags and TS key for first segment */
        skb_shinfo(seg)->tskey = skb_shinfo(gso_skb)->tskey;
        skb_shinfo(seg)->tx_flags |=
                        (skb_shinfo(gso_skb)->tx_flags & SKBTX_ANY_TSTAMP);

        /* compute checksum adjustment based on old length versus new */
        newlen = htons(sizeof(*uh) + mss);
        check = csum16_add(csum16_sub(uh->check, uh->len), newlen);

        for (;;) {
                if (copy_dtor) {
                        seg->destructor = sock_wfree;
                        seg->sk = sk;
                        sum_truesize += seg->truesize;
                }

                if (!seg->next)
                        break;

                uh->len = newlen;
                uh->check = check;

                if (seg->ip_summed == CHECKSUM_PARTIAL)
                        gso_reset_checksum(seg, ~check);
                else
                        uh->check = gso_make_checksum(seg, ~check) ? :
                                    CSUM_MANGLED_0;

                seg = seg->next;
                uh = udp_hdr(seg);
        }

        /* last packet can be partial gso_size, account for that in checksum */
        newlen = htons(skb_tail_pointer(seg) - skb_transport_header(seg) +
                       seg->data_len);
        check = csum16_add(csum16_sub(uh->check, uh->len), newlen);

        uh->len = newlen;
        uh->check = check;

        if (seg->ip_summed == CHECKSUM_PARTIAL)
                gso_reset_checksum(seg, ~check);
        else
                uh->check = gso_make_checksum(seg, ~check) ? : CSUM_MANGLED_0;

        /* update refcount for the packet */
        if (copy_dtor) {
                int 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, &sk->sk_wmem_alloc);
                else
                        WARN_ON_ONCE(refcount_sub_and_test(-delta, &sk->sk_wmem_alloc));
        }
        return segs;
}
EXPORT_SYMBOL_GPL(__udp_gso_segment);

static struct sk_buff *udp4_ufo_fragment(struct sk_buff *skb,
                                         netdev_features_t features)
{
        struct sk_buff *segs = ERR_PTR(-EINVAL);
        unsigned int mss;
        __wsum csum;
        struct udphdr *uh;
        struct iphdr *iph;

        if (skb->encapsulation &&
            (skb_shinfo(skb)->gso_type &
             (SKB_GSO_UDP_TUNNEL|SKB_GSO_UDP_TUNNEL_CSUM))) {
                segs = skb_udp_tunnel_segment(skb, features, false);
                goto out;
        }

        if (!(skb_shinfo(skb)->gso_type & (SKB_GSO_UDP | SKB_GSO_UDP_L4)))
                goto out;

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

        if (skb_shinfo(skb)->gso_type & SKB_GSO_UDP_L4)
                return __udp_gso_segment(skb, features);

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

        /* Do software UFO. Complete and fill in the UDP checksum as
         * HW cannot do checksum of UDP packets sent as multiple
         * IP fragments.
         */

        uh = udp_hdr(skb);
        iph = ip_hdr(skb);

        uh->check = 0;
        csum = skb_checksum(skb, 0, skb->len, 0);
        uh->check = udp_v4_check(skb->len, iph->saddr, iph->daddr, csum);
        if (uh->check == 0)
                uh->check = CSUM_MANGLED_0;

        skb->ip_summed = CHECKSUM_UNNECESSARY;

        /* If there is no outer header we can fake a checksum offload
         * due to the fact that we have already done the checksum in
         * software prior to segmenting the frame.
         */
        if (!skb->encap_hdr_csum)
                features |= NETIF_F_HW_CSUM;

        /* Fragment the skb. IP headers of the fragments are updated in
         * inet_gso_segment()
         */
        segs = skb_segment(skb, features);
out:
        return segs;
}

#define UDP_GRO_CNT_MAX 64
static struct sk_buff *udp_gro_receive_segment(struct list_head *head,
                                               struct sk_buff *skb)
{
        struct udphdr *uh = udp_hdr(skb);
        struct sk_buff *pp = NULL;
        struct udphdr *uh2;
        struct sk_buff *p;
        unsigned int ulen;

        /* requires non zero csum, for symmetry with GSO */
        if (!uh->check) {
                NAPI_GRO_CB(skb)->flush = 1;
                return NULL;
        }

        /* Do not deal with padded or malicious packets, sorry ! */
        ulen = ntohs(uh->len);
        if (ulen <= sizeof(*uh) || ulen != skb_gro_len(skb)) {
                NAPI_GRO_CB(skb)->flush = 1;
                return NULL;
        }
        /* pull encapsulating udp header */
        skb_gro_pull(skb, sizeof(struct udphdr));
        skb_gro_postpull_rcsum(skb, uh, sizeof(struct udphdr));

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

                uh2 = udp_hdr(p);

                /* Match ports only, as csum is always non zero */
                if ((*(u32 *)&uh->source != *(u32 *)&uh2->source)) {
                        NAPI_GRO_CB(p)->same_flow = 0;
                        continue;
                }

                /* Terminate the flow on len mismatch or if it grow "too much".
                 * Under small packet flood GRO count could elsewhere grow a lot
                 * leading to excessive truesize values.
                 * On len mismatch merge the first packet shorter than gso_size,
                 * otherwise complete the GRO packet.
                 */
                if (ulen > ntohs(uh2->len) || skb_gro_receive(p, skb) ||
                    ulen != ntohs(uh2->len) ||
                    NAPI_GRO_CB(p)->count >= UDP_GRO_CNT_MAX)
                        pp = p;

                return pp;
        }

        /* mismatch, but we never need to flush */
        return NULL;
}

INDIRECT_CALLABLE_DECLARE(struct sock *udp6_lib_lookup_skb(struct sk_buff *skb,
                                                   __be16 sport, __be16 dport));
struct sk_buff *udp_gro_receive(struct list_head *head, struct sk_buff *skb,
                                struct udphdr *uh, udp_lookup_t lookup)
{
        struct sk_buff *pp = NULL;
        struct sk_buff *p;
        struct udphdr *uh2;
        unsigned int off = skb_gro_offset(skb);
        int flush = 1;
        struct sock *sk;

        rcu_read_lock();
        sk = INDIRECT_CALL_INET(lookup, udp6_lib_lookup_skb,
                                udp4_lib_lookup_skb, skb, uh->source, uh->dest);
        if (!sk)
                goto out_unlock;

        if (udp_sk(sk)->gro_enabled) {
                pp = call_gro_receive(udp_gro_receive_segment, head, skb);
                rcu_read_unlock();
                return pp;
        }

        if (NAPI_GRO_CB(skb)->encap_mark ||
            (skb->ip_summed != CHECKSUM_PARTIAL &&
             NAPI_GRO_CB(skb)->csum_cnt == 0 &&
             !NAPI_GRO_CB(skb)->csum_valid) ||
            !udp_sk(sk)->gro_receive)
                goto out_unlock;

        /* mark that this skb passed once through the tunnel gro layer */
        NAPI_GRO_CB(skb)->encap_mark = 1;

        flush = 0;

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

                uh2 = (struct udphdr   *)(p->data + off);

                /* Match ports and either checksums are either both zero
                 * or nonzero.
                 */
                if ((*(u32 *)&uh->source != *(u32 *)&uh2->source) ||
                    (!uh->check ^ !uh2->check)) {
                        NAPI_GRO_CB(p)->same_flow = 0;
                        continue;
                }
        }

        skb_gro_pull(skb, sizeof(struct udphdr)); /* pull encapsulating udp header */
        skb_gro_postpull_rcsum(skb, uh, sizeof(struct udphdr));
        pp = call_gro_receive_sk(udp_sk(sk)->gro_receive, sk, head, skb);

out_unlock:
        rcu_read_unlock();
        skb_gro_flush_final(skb, pp, flush);
        return pp;
}
EXPORT_SYMBOL(udp_gro_receive);

INDIRECT_CALLABLE_SCOPE
struct sk_buff *udp4_gro_receive(struct list_head *head, struct sk_buff *skb)
{
        struct udphdr *uh = udp_gro_udphdr(skb);

        if (unlikely(!uh) || !static_branch_unlikely(&udp_encap_needed_key))
                goto flush;

        /* Don't bother verifying checksum if we're going to flush anyway. */
        if (NAPI_GRO_CB(skb)->flush)
                goto skip;

        if (skb_gro_checksum_validate_zero_check(skb, IPPROTO_UDP, uh->check,
                                                 inet_gro_compute_pseudo))
                goto flush;
        else if (uh->check)
                skb_gro_checksum_try_convert(skb, IPPROTO_UDP, uh->check,
                                             inet_gro_compute_pseudo);
skip:
        NAPI_GRO_CB(skb)->is_ipv6 = 0;
        return udp_gro_receive(head, skb, uh, udp4_lib_lookup_skb);

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

static int udp_gro_complete_segment(struct sk_buff *skb)
{
        struct udphdr *uh = udp_hdr(skb);

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

        skb_shinfo(skb)->gso_segs = NAPI_GRO_CB(skb)->count;
        skb_shinfo(skb)->gso_type |= SKB_GSO_UDP_L4;
        return 0;
}

int udp_gro_complete(struct sk_buff *skb, int nhoff,
                     udp_lookup_t lookup)
{
        __be16 newlen = htons(skb->len - nhoff);
        struct udphdr *uh = (struct udphdr *)(skb->data + nhoff);
        int err = -ENOSYS;
        struct sock *sk;

        uh->len = newlen;

        rcu_read_lock();
        sk = INDIRECT_CALL_INET(lookup, udp6_lib_lookup_skb,
                                udp4_lib_lookup_skb, skb, uh->source, uh->dest);
        if (sk && udp_sk(sk)->gro_enabled) {
                err = udp_gro_complete_segment(skb);
        } else if (sk && udp_sk(sk)->gro_complete) {
                skb_shinfo(skb)->gso_type = uh->check ? SKB_GSO_UDP_TUNNEL_CSUM
                                        : SKB_GSO_UDP_TUNNEL;

                /* Set encapsulation before calling into inner gro_complete()
                 * functions to make them set up the inner offsets.
                 */
                skb->encapsulation = 1;
                err = udp_sk(sk)->gro_complete(sk, skb,
                                nhoff + sizeof(struct udphdr));
        }
        rcu_read_unlock();

        if (skb->remcsum_offload)
                skb_shinfo(skb)->gso_type |= SKB_GSO_TUNNEL_REMCSUM;

        return err;
}
EXPORT_SYMBOL(udp_gro_complete);

INDIRECT_CALLABLE_SCOPE int udp4_gro_complete(struct sk_buff *skb, int nhoff)
{
        const struct iphdr *iph = ip_hdr(skb);
        struct udphdr *uh = (struct udphdr *)(skb->data + nhoff);

        if (uh->check)
                uh->check = ~udp_v4_check(skb->len - nhoff, iph->saddr,
                                          iph->daddr, 0);

        return udp_gro_complete(skb, nhoff, udp4_lib_lookup_skb);
}

static const struct net_offload udpv4_offload = {
        .callbacks = {
                .gso_segment = udp4_ufo_fragment,
                .gro_receive  = udp4_gro_receive,
                .gro_complete = udp4_gro_complete,
        },
};

int __init udpv4_offload_init(void)
{
        return inet_add_offload(&udpv4_offload, IPPROTO_UDP);
}