LXR linux/net/ipv4/gre

   1// SPDX-License-Identifier: GPL-2.0-or-later
   2/*
   3 *      IPV4 GSO/GRO offload support
   4 *      Linux INET implementation
   5 *
   6 *      GRE GSO support
   7 */
   8
   9#include <linux/skbuff.h>
  10#include <linux/init.h>
  11#include <net/protocol.h>
  12#include <net/gre.h>
  13
  14static struct sk_buff *gre_gso_segment(struct sk_buff *skb,
  15                                       netdev_features_t features)
  16{
  17        int tnl_hlen = skb_inner_mac_header(skb) - skb_transport_header(skb);
  18        bool need_csum, offload_csum, gso_partial, need_ipsec;
  19        struct sk_buff *segs = ERR_PTR(-EINVAL);
  20        u16 mac_offset = skb->mac_header;
  21        __be16 protocol = skb->protocol;
  22        u16 mac_len = skb->mac_len;
  23        int gre_offset, outer_hlen;
  24
  25        if (!skb->encapsulation)
  26                goto out;
  27
  28        if (unlikely(tnl_hlen < sizeof(struct gre_base_hdr)))
  29                goto out;
  30
  31        if (unlikely(!pskb_may_pull(skb, tnl_hlen)))
  32                goto out;
  33
  34        /* setup inner skb. */
  35        skb->encapsulation = 0;
  36        SKB_GSO_CB(skb)->encap_level = 0;
  37        __skb_pull(skb, tnl_hlen);
  38        skb_reset_mac_header(skb);
  39        skb_set_network_header(skb, skb_inner_network_offset(skb));
  40        skb->mac_len = skb_inner_network_offset(skb);
  41        skb->protocol = skb->inner_protocol;
  42
  43        need_csum = !!(skb_shinfo(skb)->gso_type & SKB_GSO_GRE_CSUM);
  44        skb->encap_hdr_csum = need_csum;
  45
  46        features &= skb->dev->hw_enc_features;
  47        if (need_csum)
  48                features &= ~NETIF_F_SCTP_CRC;
  49
  50        need_ipsec = skb_dst(skb) && dst_xfrm(skb_dst(skb));
  51        /* Try to offload checksum if possible */
  52        offload_csum = !!(need_csum && !need_ipsec &&
  53                          (skb->dev->features & NETIF_F_HW_CSUM));
  54
  55        /* segment inner packet. */
  56        segs = skb_mac_gso_segment(skb, features);
  57        if (IS_ERR_OR_NULL(segs)) {
  58                skb_gso_error_unwind(skb, protocol, tnl_hlen, mac_offset,
  59                                     mac_len);
  60                goto out;
  61        }
  62
  63        gso_partial = !!(skb_shinfo(segs)->gso_type & SKB_GSO_PARTIAL);
  64
  65        outer_hlen = skb_tnl_header_len(skb);
  66        gre_offset = outer_hlen - tnl_hlen;
  67        skb = segs;
  68        do {
  69                struct gre_base_hdr *greh;
  70                __sum16 *pcsum;
  71
  72                /* Set up inner headers if we are offloading inner checksum */
  73                if (skb->ip_summed == CHECKSUM_PARTIAL) {
  74                        skb_reset_inner_headers(skb);
  75                        skb->encapsulation = 1;
  76                }
  77
  78                skb->mac_len = mac_len;
  79                skb->protocol = protocol;
  80
  81                __skb_push(skb, outer_hlen);
  82                skb_reset_mac_header(skb);
  83                skb_set_network_header(skb, mac_len);
  84                skb_set_transport_header(skb, gre_offset);
  85
  86                if (!need_csum)
  87                        continue;
  88
  89                greh = (struct gre_base_hdr *)skb_transport_header(skb);
  90                pcsum = (__sum16 *)(greh + 1);
  91
  92                if (gso_partial && skb_is_gso(skb)) {
  93                        unsigned int partial_adj;
  94
  95                        /* Adjust checksum to account for the fact that
  96                         * the partial checksum is based on actual size
  97                         * whereas headers should be based on MSS size.
  98                         */
  99                        partial_adj = skb->len + skb_headroom(skb) -
 100                                      SKB_GSO_CB(skb)->data_offset -
 101                                      skb_shinfo(skb)->gso_size;
 102                        *pcsum = ~csum_fold((__force __wsum)htonl(partial_adj));
 103                } else {
 104                        *pcsum = 0;
 105                }
 106
 107                *(pcsum + 1) = 0;
 108                if (skb->encapsulation || !offload_csum) {
 109                        *pcsum = gso_make_checksum(skb, 0);
 110                } else {
 111                        skb->ip_summed = CHECKSUM_PARTIAL;
 112                        skb->csum_start = skb_transport_header(skb) - skb->head;
 113                        skb->csum_offset = sizeof(*greh);
 114                }
 115        } while ((skb = skb->next));
 116out:
 117        return segs;
 118}
 119
 120static struct sk_buff *gre_gro_receive(struct list_head *head,
 121                                       struct sk_buff *skb)
 122{
 123        struct sk_buff *pp = NULL;
 124        struct sk_buff *p;
 125        const struct gre_base_hdr *greh;
 126        unsigned int hlen, grehlen;
 127        unsigned int off;
 128        int flush = 1;
 129        struct packet_offload *ptype;
 130        __be16 type;
 131
 132        if (NAPI_GRO_CB(skb)->encap_mark)
 133                goto out;
 134
 135        NAPI_GRO_CB(skb)->encap_mark = 1;
 136
 137        off = skb_gro_offset(skb);
 138        hlen = off + sizeof(*greh);
 139        greh = skb_gro_header_fast(skb, off);
 140        if (skb_gro_header_hard(skb, hlen)) {
 141                greh = skb_gro_header_slow(skb, hlen, off);
 142                if (unlikely(!greh))
 143                        goto out;
 144        }
 145
 146        /* Only support version 0 and K (key), C (csum) flags. Note that
 147         * although the support for the S (seq#) flag can be added easily
 148         * for GRO, this is problematic for GSO hence can not be enabled
 149         * here because a GRO pkt may end up in the forwarding path, thus
 150         * requiring GSO support to break it up correctly.
 151         */
 152        if ((greh->flags & ~(GRE_KEY|GRE_CSUM)) != 0)
 153                goto out;
 154
 155        /* We can only support GRE_CSUM if we can track the location of
 156         * the GRE header.  In the case of FOU/GUE we cannot because the
 157         * outer UDP header displaces the GRE header leaving us in a state
 158         * of limbo.
 159         */
 160        if ((greh->flags & GRE_CSUM) && NAPI_GRO_CB(skb)->is_fou)
 161                goto out;
 162
 163        type = greh->protocol;
 164
 165        rcu_read_lock();
 166        ptype = gro_find_receive_by_type(type);
 167        if (!ptype)
 168                goto out_unlock;
 169
 170        grehlen = GRE_HEADER_SECTION;
 171
 172        if (greh->flags & GRE_KEY)
 173                grehlen += GRE_HEADER_SECTION;
 174
 175        if (greh->flags & GRE_CSUM)
 176                grehlen += GRE_HEADER_SECTION;
 177
 178        hlen = off + grehlen;
 179        if (skb_gro_header_hard(skb, hlen)) {
 180                greh = skb_gro_header_slow(skb, hlen, off);
 181                if (unlikely(!greh))
 182                        goto out_unlock;
 183        }
 184
 185        /* Don't bother verifying checksum if we're going to flush anyway. */
 186        if ((greh->flags & GRE_CSUM) && !NAPI_GRO_CB(skb)->flush) {
 187                if (skb_gro_checksum_simple_validate(skb))
 188                        goto out_unlock;
 189
 190                skb_gro_checksum_try_convert(skb, IPPROTO_GRE,
 191                                             null_compute_pseudo);
 192        }
 193
 194        list_for_each_entry(p, head, list) {
 195                const struct gre_base_hdr *greh2;
 196
 197                if (!NAPI_GRO_CB(p)->same_flow)
 198                        continue;
 199
 200                /* The following checks are needed to ensure only pkts
 201                 * from the same tunnel are considered for aggregation.
 202                 * The criteria for "the same tunnel" includes:
 203                 * 1) same version (we only support version 0 here)
 204                 * 2) same protocol (we only support ETH_P_IP for now)
 205                 * 3) same set of flags
 206                 * 4) same key if the key field is present.
 207                 */
 208                greh2 = (struct gre_base_hdr *)(p->data + off);
 209
 210                if (greh2->flags != greh->flags ||
 211                    greh2->protocol != greh->protocol) {
 212                        NAPI_GRO_CB(p)->same_flow = 0;
 213                        continue;
 214                }
 215                if (greh->flags & GRE_KEY) {
 216                        /* compare keys */
 217                        if (*(__be32 *)(greh2+1) != *(__be32 *)(greh+1)) {
 218                                NAPI_GRO_CB(p)->same_flow = 0;
 219                                continue;
 220                        }
 221                }
 222        }
 223
 224        skb_gro_pull(skb, grehlen);
 225
 226        /* Adjusted NAPI_GRO_CB(skb)->csum after skb_gro_pull()*/
 227        skb_gro_postpull_rcsum(skb, greh, grehlen);
 228
 229        pp = call_gro_receive(ptype->callbacks.gro_receive, head, skb);
 230        flush = 0;
 231
 232out_unlock:
 233        rcu_read_unlock();
 234out:
 235        skb_gro_flush_final(skb, pp, flush);
 236
 237        return pp;
 238}
 239
 240static int gre_gro_complete(struct sk_buff *skb, int nhoff)
 241{
 242        struct gre_base_hdr *greh = (struct gre_base_hdr *)(skb->data + nhoff);
 243        struct packet_offload *ptype;
 244        unsigned int grehlen = sizeof(*greh);
 245        int err = -ENOENT;
 246        __be16 type;
 247
 248        skb->encapsulation = 1;
 249        skb_shinfo(skb)->gso_type = SKB_GSO_GRE;
 250
 251        type = greh->protocol;
 252        if (greh->flags & GRE_KEY)
 253                grehlen += GRE_HEADER_SECTION;
 254
 255        if (greh->flags & GRE_CSUM)
 256                grehlen += GRE_HEADER_SECTION;
 257
 258        rcu_read_lock();
 259        ptype = gro_find_complete_by_type(type);
 260        if (ptype)
 261                err = ptype->callbacks.gro_complete(skb, nhoff + grehlen);
 262
 263        rcu_read_unlock();
 264
 265        skb_set_inner_mac_header(skb, nhoff + grehlen);
 266
 267        return err;
 268}
 269
 270static const struct net_offload gre_offload = {
 271        .callbacks = {
 272                .gso_segment = gre_gso_segment,
 273                .gro_receive = gre_gro_receive,
 274                .gro_complete = gre_gro_complete,
 275        },
 276};
 277
 278static int __init gre_offload_init(void)
 279{
 280        int err;
 281
 282        err = inet_add_offload(&gre_offload, IPPROTO_GRE);
 283#if IS_ENABLED(CONFIG_IPV6)
 284        if (err)
 285                return err;
 286
 287        err = inet6_add_offload(&gre_offload, IPPROTO_GRE);
 288        if (err)
 289                inet_del_offload(&gre_offload, IPPROTO_GRE);
 290#endif
 291
 292        return err;
 293}
 294device_initcall(gre_offload_init);
 295