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         /* UDP Tunnel offload on ipv6 is not yet supported. */
  25         if (skb->encapsulation)
  26                 return -EINVAL;
  27
  28         if (!pskb_may_pull(skb, sizeof(*uh)))
  29                 return -EINVAL;
  30
  31         ipv6h = ipv6_hdr(skb);
  32         uh = udp_hdr(skb);
  33
  34         uh->check = ~csum_ipv6_magic(&ipv6h->saddr, &ipv6h->daddr, skb->len,
  35                                      IPPROTO_UDP, 0);
  36         skb->csum_start = skb_transport_header(skb) - skb->head;
  37         skb->csum_offset = offsetof(struct udphdr, check);
  38         skb->ip_summed = CHECKSUM_PARTIAL;
  39         return 0;
  40 }
  41
  42 static struct sk_buff *udp6_ufo_fragment(struct sk_buff *skb,
  43         netdev_features_t features)
  44 {
  45         struct sk_buff *segs = ERR_PTR(-EINVAL);
  46         unsigned int mss;
  47         unsigned int unfrag_ip6hlen, unfrag_len;
  48         struct frag_hdr *fptr;
  49         u8 *packet_start, *prevhdr;
  50         u8 nexthdr;
  51         u8 frag_hdr_sz = sizeof(struct frag_hdr);
  52         int offset;
  53         __wsum csum;
  54         int tnl_hlen;
  55
  56         mss = skb_shinfo(skb)->gso_size;
  57         if (unlikely(skb->len <= mss))
  58                 goto out;
  59
  60         if (skb_gso_ok(skb, features | NETIF_F_GSO_ROBUST)) {
  61                 /* Packet is from an untrusted source, reset gso_segs. */
  62                 int type = skb_shinfo(skb)->gso_type;
  63
  64                 if (unlikely(type & ~(SKB_GSO_UDP |
  65                                       SKB_GSO_DODGY |
  66                                       SKB_GSO_UDP_TUNNEL |
  67                                       SKB_GSO_GRE |
  68                                       SKB_GSO_MPLS) ||
  69                              !(type & (SKB_GSO_UDP))))
  70                         goto out;
  71
  72                 skb_shinfo(skb)->gso_segs = DIV_ROUND_UP(skb->len, mss);
  73
  74                 segs = NULL;
  75                 goto out;
  76         }
  77
  78         /* Do software UFO. Complete and fill in the UDP checksum as HW cannot
  79          * do checksum of UDP packets sent as multiple IP fragments.
  80          */
  81         offset = skb_checksum_start_offset(skb);
  82         csum = skb_checksum(skb, offset, skb->len - offset, 0);
  83         offset += skb->csum_offset;
  84         *(__sum16 *)(skb->data + offset) = csum_fold(csum);
  85         skb->ip_summed = CHECKSUM_NONE;
  86
  87         /* Check if there is enough headroom to insert fragment header. */
  88         tnl_hlen = skb_tnl_header_len(skb);
  89         if (skb_headroom(skb) < (tnl_hlen + frag_hdr_sz)) {
  90                 if (gso_pskb_expand_head(skb, tnl_hlen + frag_hdr_sz))
  91                         goto out;
  92         }
  93
  94         /* Find the unfragmentable header and shift it left by frag_hdr_sz
  95          * bytes to insert fragment header.
  96          */
  97         unfrag_ip6hlen = ip6_find_1stfragopt(skb, &prevhdr);
  98         nexthdr = *prevhdr;
  99         *prevhdr = NEXTHDR_FRAGMENT;
 100         unfrag_len = (skb_network_header(skb) - skb_mac_header(skb)) +
 101                      unfrag_ip6hlen + tnl_hlen;
 102         packet_start = (u8 *) skb->head + SKB_GSO_CB(skb)->mac_offset;
 103         memmove(packet_start-frag_hdr_sz, packet_start, unfrag_len);
 104
 105         SKB_GSO_CB(skb)->mac_offset -= frag_hdr_sz;
 106         skb->mac_header -= frag_hdr_sz;
 107         skb->network_header -= frag_hdr_sz;
 108
 109         fptr = (struct frag_hdr *)(skb_network_header(skb) + unfrag_ip6hlen);
 110         fptr->nexthdr = nexthdr;
 111         fptr->reserved = 0;
 112         ipv6_select_ident(fptr, (struct rt6_info *)skb_dst(skb));
 113
 114         /* Fragment the skb. ipv6 header and the remaining fields of the
 115          * fragment header are updated in ipv6_gso_segment()
 116          */
 117         segs = skb_segment(skb, features);
 118
 119 out:
 120         return segs;
 121 }
 122 static const struct net_offload udpv6_offload = {
 123         .callbacks = {
 124                 .gso_send_check =       udp6_ufo_send_check,
 125                 .gso_segment    =       udp6_ufo_fragment,
 126         },
 127 };
 128
 129 int __init udp_offload_init(void)
 130 {
 131         return inet6_add_offload(&udpv6_offload, IPPROTO_UDP);
 132 }