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