LXR linux/net/ipv6/udp

   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
  19static 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
  41static struct sk_buff *udp6_ufo_fragment(struct sk_buff *skb,
  42                                         netdev_features_t features)
  43{
  44        struct sk_buff *segs = ERR_PTR(-EINVAL);
  45        unsigned int mss;
  46        unsigned int unfrag_ip6hlen, unfrag_len;
  47        struct frag_hdr *fptr;
  48        u8 *packet_start, *prevhdr;
  49        u8 nexthdr;
  50        u8 frag_hdr_sz = sizeof(struct frag_hdr);
  51        int offset;
  52        __wsum csum;
  53        int tnl_hlen;
  54
  55        mss = skb_shinfo(skb)->gso_size;
  56        if (unlikely(skb->len <= mss))
  57                goto out;
  58
  59        if (skb_gso_ok(skb, features | NETIF_F_GSO_ROBUST)) {
  60                /* Packet is from an untrusted source, reset gso_segs. */
  61                int type = skb_shinfo(skb)->gso_type;
  62
  63                if (unlikely(type & ~(SKB_GSO_UDP |
  64                                      SKB_GSO_DODGY |
  65                                      SKB_GSO_UDP_TUNNEL |
  66                                      SKB_GSO_GRE |
  67                                      SKB_GSO_MPLS) ||
  68                             !(type & (SKB_GSO_UDP))))
  69                        goto out;
  70
  71                skb_shinfo(skb)->gso_segs = DIV_ROUND_UP(skb->len, mss);
  72
  73                segs = NULL;
  74                goto out;
  75        }
  76
  77        if (skb->encapsulation && skb_shinfo(skb)->gso_type & SKB_GSO_UDP_TUNNEL)
  78                segs = skb_udp_tunnel_segment(skb, features);
  79        else {
  80                /* Do software UFO. Complete and fill in the UDP checksum as HW cannot
  81                 * do checksum of UDP packets sent as multiple IP fragments.
  82                 */
  83                offset = skb_checksum_start_offset(skb);
  84                csum = skb_checksum(skb, offset, skb->len - offset, 0);
  85                offset += skb->csum_offset;
  86                *(__sum16 *)(skb->data + offset) = csum_fold(csum);
  87                skb->ip_summed = CHECKSUM_NONE;
  88
  89                /* Check if there is enough headroom to insert fragment header. */
  90                tnl_hlen = skb_tnl_header_len(skb);
  91                if (skb_headroom(skb) < (tnl_hlen + frag_hdr_sz)) {
  92                        if (gso_pskb_expand_head(skb, tnl_hlen + frag_hdr_sz))
  93                                goto out;
  94                }
  95
  96                /* Find the unfragmentable header and shift it left by frag_hdr_sz
  97                 * bytes to insert fragment header.
  98                 */
  99                unfrag_ip6hlen = ip6_find_1stfragopt(skb, &prevhdr);
 100                nexthdr = *prevhdr;
 101                *prevhdr = NEXTHDR_FRAGMENT;
 102                unfrag_len = (skb_network_header(skb) - skb_mac_header(skb)) +
 103                             unfrag_ip6hlen + tnl_hlen;
 104                packet_start = (u8 *) skb->head + SKB_GSO_CB(skb)->mac_offset;
 105                memmove(packet_start-frag_hdr_sz, packet_start, unfrag_len);
 106
 107                SKB_GSO_CB(skb)->mac_offset -= frag_hdr_sz;
 108                skb->mac_header -= frag_hdr_sz;
 109                skb->network_header -= frag_hdr_sz;
 110
 111                fptr = (struct frag_hdr *)(skb_network_header(skb) + unfrag_ip6hlen);
 112                fptr->nexthdr = nexthdr;
 113                fptr->reserved = 0;
 114                ipv6_select_ident(fptr, (struct rt6_info *)skb_dst(skb));
 115
 116                /* Fragment the skb. ipv6 header and the remaining fields of the
 117                 * fragment header are updated in ipv6_gso_segment()
 118                 */
 119                segs = skb_segment(skb, features);
 120        }
 121
 122out:
 123        return segs;
 124}
 125static const struct net_offload udpv6_offload = {
 126        .callbacks = {
 127                .gso_send_check =       udp6_ufo_send_check,
 128                .gso_segment    =       udp6_ufo_fragment,
 129        },
 130};
 131
 132int __init udp_offload_init(void)
 133{
 134        return inet6_add_offload(&udpv6_offload, IPPROTO_UDP);
 135}
 136