net/ipv4/udp_offload.c

   1 /*
   2  *      IPV4 GSO/GRO offload support
   3  *      Linux INET 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  *      UDPv4 GSO support
  11  */
  12
  13 #include <linux/skbuff.h>
  14 #include <net/udp.h>
  15 #include <net/protocol.h>
  16
  17 static int udp4_ufo_send_check(struct sk_buff *skb)
  18 {
  19         if (!pskb_may_pull(skb, sizeof(struct udphdr)))
  20                 return -EINVAL;
  21
  22         if (likely(!skb->encapsulation)) {
  23                 const struct iphdr *iph;
  24                 struct udphdr *uh;
  25
  26                 iph = ip_hdr(skb);
  27                 uh = udp_hdr(skb);
  28
  29                 uh->check = ~csum_tcpudp_magic(iph->saddr, iph->daddr, skb->len,
  30                                 IPPROTO_UDP, 0);
  31                 skb->csum_start = skb_transport_header(skb) - skb->head;
  32                 skb->csum_offset = offsetof(struct udphdr, check);
  33                 skb->ip_summed = CHECKSUM_PARTIAL;
  34         }
  35
  36         return 0;
  37 }
  38
  39 static struct sk_buff *udp4_ufo_fragment(struct sk_buff *skb,
  40                                          netdev_features_t features)
  41 {
  42         struct sk_buff *segs = ERR_PTR(-EINVAL);
  43         unsigned int mss;
  44         int offset;
  45         __wsum csum;
  46
  47         if (skb->encapsulation &&
  48             skb_shinfo(skb)->gso_type & SKB_GSO_UDP_TUNNEL) {
  49                 segs = skb_udp_tunnel_segment(skb, features);
  50                 goto out;
  51         }
  52
  53         mss = skb_shinfo(skb)->gso_size;
  54         if (unlikely(skb->len <= mss))
  55                 goto out;
  56
  57         if (skb_gso_ok(skb, features | NETIF_F_GSO_ROBUST)) {
  58                 /* Packet is from an untrusted source, reset gso_segs. */
  59                 int type = skb_shinfo(skb)->gso_type;
  60
  61                 if (unlikely(type & ~(SKB_GSO_UDP | SKB_GSO_DODGY |
  62                                       SKB_GSO_UDP_TUNNEL |
  63                                       SKB_GSO_GRE | SKB_GSO_MPLS) ||
  64                              !(type & (SKB_GSO_UDP))))
  65                         goto out;
  66
  67                 skb_shinfo(skb)->gso_segs = DIV_ROUND_UP(skb->len, mss);
  68
  69                 segs = NULL;
  70                 goto out;
  71         }
  72
  73         /* Do software UFO. Complete and fill in the UDP checksum as
  74          * HW cannot do checksum of UDP packets sent as multiple
  75          * IP fragments.
  76          */
  77         offset = skb_checksum_start_offset(skb);
  78         csum = skb_checksum(skb, offset, skb->len - offset, 0);
  79         offset += skb->csum_offset;
  80         *(__sum16 *)(skb->data + offset) = csum_fold(csum);
  81         skb->ip_summed = CHECKSUM_NONE;
  82
  83         /* Fragment the skb. IP headers of the fragments are updated in
  84          * inet_gso_segment()
  85          */
  86         segs = skb_segment(skb, features);
  87 out:
  88         return segs;
  89 }
  90
  91 static const struct net_offload udpv4_offload = {
  92         .callbacks = {
  93                 .gso_send_check = udp4_ufo_send_check,
  94                 .gso_segment = udp4_ufo_fragment,
  95         },
  96 };
  97
  98 int __init udpv4_offload_init(void)
  99 {
 100         return inet_add_offload(&udpv4_offload, IPPROTO_UDP);
 101 }