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 *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
 122 out:
 123         return segs;
 124 }
 125 static 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
 132 int __init udp_offload_init(void)
 133 {
 134         return inet6_add_offload(&udpv6_offload, IPPROTO_UDP);
 135 }