include/xen/net-util.h

   1 #ifndef __XEN_NETUTIL_H__
   2 #define __XEN_NETUTIL_H__
   3
   4 #include <linux/kernel.h>
   5 #include <linux/skbuff.h>
   6 #include <linux/tcp.h>
   7 #include <linux/udp.h>
   8 #include <net/ip.h>
   9
  10 static inline int skb_checksum_setup(struct sk_buff *skb,
  11                                      unsigned long *fixup_counter)
  12 {
  13         struct iphdr *iph = (void *)skb->data;
  14         unsigned char *th;
  15         __be16 *csum = NULL;
  16         int err = -EPROTO;
  17
  18         if (skb->ip_summed != CHECKSUM_PARTIAL) {
  19                 /* A non-CHECKSUM_PARTIAL SKB does not require setup. */
  20                 if (!skb_is_gso(skb))
  21                         return 0;
  22
  23                 /*
  24                  * A GSO SKB must be CHECKSUM_PARTIAL. However some buggy
  25                  * peers can fail to set NETRXF_csum_blank when sending a GSO
  26                  * frame. In this case force the SKB to CHECKSUM_PARTIAL and
  27                  * recalculate the partial checksum.
  28                  */
  29                 ++*fixup_counter;
  30                 --csum;
  31         }
  32
  33         if (skb->protocol != htons(ETH_P_IP))
  34                 goto out;
  35
  36         th = skb->data + 4 * iph->ihl;
  37         if (th >= skb_tail_pointer(skb))
  38                 goto out;
  39
  40         skb->csum_start = th - skb->head;
  41         switch (iph->protocol) {
  42         case IPPROTO_TCP:
  43                 skb->csum_offset = offsetof(struct tcphdr, check);
  44                 if (csum)
  45                         csum = &((struct tcphdr *)th)->check;
  46                 break;
  47         case IPPROTO_UDP:
  48                 skb->csum_offset = offsetof(struct udphdr, check);
  49                 if (csum)
  50                         csum = &((struct udphdr *)th)->check;
  51                 break;
  52         default:
  53                 if (net_ratelimit())
  54                         pr_err("Attempting to checksum a non-"
  55                                "TCP/UDP packet, dropping a protocol"
  56                                " %d packet\n", iph->protocol);
  57                 goto out;
  58         }
  59
  60         if ((th + skb->csum_offset + sizeof(*csum)) > skb_tail_pointer(skb))
  61                 goto out;
  62
  63         if (csum) {
  64                 *csum = ~csum_tcpudp_magic(iph->saddr, iph->daddr,
  65                                            skb->len - iph->ihl*4,
  66                                            IPPROTO_TCP, 0);
  67                 skb->ip_summed = CHECKSUM_PARTIAL;
  68         }
  69
  70         err = 0;
  71 out:
  72         return err;
  73 }
  74
  75 #endif /* __XEN_NETUTIL_H__ */