net/ipv6/udp_offload.c

   1 /*
   2  *      IPV6 GSO/GRO offload support
   3  *      Linux INET6 implementation
   4  *
   5  *      This program is free software; you can redistribute it and/or
   6  *      modify it under the terms of the GNU General Public License
   7  *      as published by the Free Software Foundation; either version
   8  *      2 of the License, or (at your option) any later version.
   9  *
  10  *      UDPv6 GSO support
  11  */
  12 #include <linux/skbuff.h>
  13 #include <net/protocol.h>
  14 #include <net/ipv6.h>
  15 #include <net/udp.h>
  16 #include <net/ip6_checksum.h>
  17 #include "ip6_offload.h"
  18
  19 static int udp6_ufo_send_check(struct sk_buff *skb)
  20 {
  21         const struct ipv6hdr *ipv6h;
  22         struct udphdr *uh;
  23
  24         if (!pskb_may_pull(skb, sizeof(*uh)))
  25                 return -EINVAL;
  26
  27         if (likely(!skb->encapsulation)) {
  28                 ipv6h = ipv6_hdr(skb);
  29                 uh = udp_hdr(skb);
  30
  31                 uh->check = ~csum_ipv6_magic(&ipv6h->saddr, &ipv6h->daddr, skb->len,
  32                                              IPPROTO_UDP, 0);
  33                 skb->csum_start = skb_transport_header(skb) - skb->head;
  34                 skb->csum_offset = offsetof(struct udphdr, check);
  35                 skb->ip_summed = CHECKSUM_PARTIAL;
  36         }
  37
  38         return 0;
  39 }
  40
  41 static struct sk_buff *skb_udp6_tunnel_segment(struct sk_buff *skb,
  42                                                netdev_features_t features)
  43 {
  44         struct sk_buff *segs = ERR_PTR(-EINVAL);
  45         int mac_len = skb->mac_len;
  46         int tnl_hlen = skb_inner_mac_header(skb) - skb_transport_header(skb);
  47         int outer_hlen;
  48         netdev_features_t enc_features;
  49
  50         if (unlikely(!pskb_may_pull(skb, tnl_hlen)))
  51                 goto out;
  52
  53         skb->encapsulation = 0;
  54         __skb_pull(skb, tnl_hlen);
  55         skb_reset_mac_header(skb);
  56         skb_set_network_header(skb, skb_inner_network_offset(skb));
  57         skb->mac_len = skb_inner_network_offset(skb);
  58
  59         /* segment inner packet. */
  60         enc_features = skb->dev->hw_enc_features & netif_skb_features(skb);
  61         segs = skb_mac_gso_segment(skb, enc_features);
  62         if (!segs || IS_ERR(segs))
  63                 goto out;
  64
  65         outer_hlen = skb_tnl_header_len(skb);
  66         skb = segs;
  67         do {
  68                 struct udphdr *uh;
  69                 struct ipv6hdr *ipv6h;
  70                 int udp_offset = outer_hlen - tnl_hlen;
  71                 u32 len;
  72
  73                 skb->mac_len = mac_len;
  74
  75                 skb_push(skb, outer_hlen);
  76                 skb_reset_mac_header(skb);
  77                 skb_set_network_header(skb, mac_len);
  78                 skb_set_transport_header(skb, udp_offset);
  79                 uh = udp_hdr(skb);
  80                 uh->len = htons(skb->len - udp_offset);
  81                 ipv6h = ipv6_hdr(skb);
  82                 len = skb->len - udp_offset;
  83
  84                 uh->check = ~csum_ipv6_magic(&ipv6h->saddr, &ipv6h->daddr,
  85                                              len, IPPROTO_UDP, 0);
  86                 uh->check = csum_fold(skb_checksum(skb, udp_offset, len, 0));
  87                 if (uh->check == 0)
  88                         uh->check = CSUM_MANGLED_0;
  89                 skb->ip_summed = CHECKSUM_NONE;
  90         } while ((skb = skb->next));
  91 out:
  92         return segs;
  93 }
  94
  95 static struct sk_buff *udp6_ufo_fragment(struct sk_buff *skb,
  96                                          netdev_features_t features)
  97 {
  98         struct sk_buff *segs = ERR_PTR(-EINVAL);
  99         unsigned int mss;
 100         unsigned int unfrag_ip6hlen, unfrag_len;
 101         struct frag_hdr *fptr;
 102         u8 *packet_start, *prevhdr;
 103         u8 nexthdr;
 104         u8 frag_hdr_sz = sizeof(struct frag_hdr);
 105         int offset;
 106         __wsum csum;
 107         int tnl_hlen;
 108
 109         mss = skb_shinfo(skb)->gso_size;
 110         if (unlikely(skb->len <= mss))
 111                 goto out;
 112
 113         if (skb_gso_ok(skb, features | NETIF_F_GSO_ROBUST)) {
 114                 /* Packet is from an untrusted source, reset gso_segs. */
 115                 int type = skb_shinfo(skb)->gso_type;
 116
 117                 if (unlikely(type & ~(SKB_GSO_UDP |
 118                                       SKB_GSO_DODGY |
 119                                       SKB_GSO_UDP_TUNNEL |
 120                                       SKB_GSO_GRE |
 121                                       SKB_GSO_MPLS) ||
 122                              !(type & (SKB_GSO_UDP))))
 123                         goto out;
 124
 125                 skb_shinfo(skb)->gso_segs = DIV_ROUND_UP(skb->len, mss);
 126
 127                 segs = NULL;
 128                 goto out;
 129         }
 130
 131         if (skb->encapsulation && skb_shinfo(skb)->gso_type & SKB_GSO_UDP_TUNNEL)
 132                 segs = skb_udp6_tunnel_segment(skb, features);
 133         else {
 134                 /* Do software UFO. Complete and fill in the UDP checksum as HW cannot
 135                  * do checksum of UDP packets sent as multiple IP fragments.
 136                  */
 137                 offset = skb_checksum_start_offset(skb);
 138                 csum = skb_checksum(skb, offset, skb->len - offset, 0);
 139                 offset += skb->csum_offset;
 140                 *(__sum16 *)(skb->data + offset) = csum_fold(csum);
 141                 skb->ip_summed = CHECKSUM_NONE;
 142
 143                 /* Check if there is enough headroom to insert fragment header. */
 144                 tnl_hlen = skb_tnl_header_len(skb);
 145                 if (skb_headroom(skb) < (tnl_hlen + frag_hdr_sz)) {
 146                         if (gso_pskb_expand_head(skb, tnl_hlen + frag_hdr_sz))
 147                                 goto out;
 148                 }
 149
 150                 /* Find the unfragmentable header and shift it left by frag_hdr_sz
 151                  * bytes to insert fragment header.
 152                  */
 153                 unfrag_ip6hlen = ip6_find_1stfragopt(skb, &prevhdr);
 154                 nexthdr = *prevhdr;
 155                 *prevhdr = NEXTHDR_FRAGMENT;
 156                 unfrag_len = (skb_network_header(skb) - skb_mac_header(skb)) +
 157                              unfrag_ip6hlen + tnl_hlen;
 158                 packet_start = (u8 *) skb->head + SKB_GSO_CB(skb)->mac_offset;
 159                 memmove(packet_start-frag_hdr_sz, packet_start, unfrag_len);
 160
 161                 SKB_GSO_CB(skb)->mac_offset -= frag_hdr_sz;
 162                 skb->mac_header -= frag_hdr_sz;
 163                 skb->network_header -= frag_hdr_sz;
 164
 165                 fptr = (struct frag_hdr *)(skb_network_header(skb) + unfrag_ip6hlen);
 166                 fptr->nexthdr = nexthdr;
 167                 fptr->reserved = 0;
 168                 ipv6_select_ident(fptr, (struct rt6_info *)skb_dst(skb));
 169
 170                 /* Fragment the skb. ipv6 header and the remaining fields of the
 171                  * fragment header are updated in ipv6_gso_segment()
 172                  */
 173                 segs = skb_segment(skb, features);
 174         }
 175
 176 out:
 177         return segs;
 178 }
 179 static const struct net_offload udpv6_offload = {
 180         .callbacks = {
 181                 .gso_send_check =       udp6_ufo_send_check,
 182                 .gso_segment    =       udp6_ufo_fragment,
 183         },
 184 };
 185
 186 int __init udp_offload_init(void)
 187 {
 188         return inet6_add_offload(&udpv6_offload, IPPROTO_UDP);
 189 }