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        /* 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
  42static 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                             !(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        /* Do software UFO. Complete and fill in the UDP checksum as HW cannot
  78         * do checksum of UDP packets sent as multiple IP fragments.
  79         */
  80        offset = skb_checksum_start_offset(skb);
  81        csum = skb_checksum(skb, offset, skb->len - offset, 0);
  82        offset += skb->csum_offset;
  83        *(__sum16 *)(skb->data + offset) = csum_fold(csum);
  84        skb->ip_summed = CHECKSUM_NONE;
  85
  86        /* Check if there is enough headroom to insert fragment header. */
  87        tnl_hlen = skb_tnl_header_len(skb);
  88        if (skb_headroom(skb) < (tnl_hlen + frag_hdr_sz)) {
  89                if (gso_pskb_expand_head(skb, tnl_hlen + frag_hdr_sz))
  90                        goto out;
  91        }
  92
  93        /* Find the unfragmentable header and shift it left by frag_hdr_sz
  94         * bytes to insert fragment header.
  95         */
  96        unfrag_ip6hlen = ip6_find_1stfragopt(skb, &prevhdr);
  97        nexthdr = *prevhdr;
  98        *prevhdr = NEXTHDR_FRAGMENT;
  99        unfrag_len = (skb_network_header(skb) - skb_mac_header(skb)) +
 100                     unfrag_ip6hlen + tnl_hlen;
 101        packet_start = (u8 *) skb->head + SKB_GSO_CB(skb)->mac_offset;
 102        memmove(packet_start-frag_hdr_sz, packet_start, unfrag_len);
 103
 104        SKB_GSO_CB(skb)->mac_offset -= frag_hdr_sz;
 105        skb->mac_header -= frag_hdr_sz;
 106        skb->network_header -= frag_hdr_sz;
 107
 108        fptr = (struct frag_hdr *)(skb_network_header(skb) + unfrag_ip6hlen);
 109        fptr->nexthdr = nexthdr;
 110        fptr->reserved = 0;
 111        ipv6_select_ident(fptr, (struct rt6_info *)skb_dst(skb));
 112
 113        /* Fragment the skb. ipv6 header and the remaining fields of the
 114         * fragment header are updated in ipv6_gso_segment()
 115         */
 116        segs = skb_segment(skb, features);
 117
 118out:
 119        return segs;
 120}
 121static const struct net_offload udpv6_offload = {
 122        .callbacks = {
 123                .gso_send_check =       udp6_ufo_send_check,
 124                .gso_segment    =       udp6_ufo_fragment,
 125        },
 126};
 127
 128int __init udp_offload_init(void)
 129{
 130        return inet6_add_offload(&udpv6_offload, IPPROTO_UDP);
 131}
 132