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authorHerbert Xu <herbert@gondor.apana.org.au>2007-04-09 14:59:07 -0400
committerDavid S. Miller <davem@sunset.davemloft.net>2007-04-26 01:28:40 -0400
commit663ead3bb8d5b561e70fc3bb3861c9220b5a77eb (patch)
tree551d031fc9c904487ced4d8d3363e5ed8f369794 /net/ipv6/tcp_ipv6.c
parentac758e3c55c529714354fc268892ca4d23ca1e99 (diff)
[NET]: Use csum_start offset instead of skb_transport_header
The skb transport pointer is currently used to specify the start of the checksum region for transmit checksum offload. Unfortunately, the same pointer is also used during receive side processing. This creates a problem when we want to retransmit a received packet with partial checksums since the skb transport pointer would be overwritten. This patch solves this problem by creating a new 16-bit csum_start offset value to replace the skb transport header for the purpose of checksums. This offset is calculated from skb->head so that it does not have to change when skb->data changes. No extra space is required since csum_offset itself fits within a 16-bit word so we can use the other 16 bits for csum_start. For backwards compatibility, just before we push a packet with partial checksums off into the device driver, we set the skb transport header to what it would have been under the old scheme. Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/ipv6/tcp_ipv6.c')
-rw-r--r--net/ipv6/tcp_ipv6.c2
1 files changed, 2 insertions, 0 deletions
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index 4a55da079f5f..7e824b97126d 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -950,6 +950,7 @@ static void tcp_v6_send_check(struct sock *sk, int len, struct sk_buff *skb)
950 950
951 if (skb->ip_summed == CHECKSUM_PARTIAL) { 951 if (skb->ip_summed == CHECKSUM_PARTIAL) {
952 th->check = ~csum_ipv6_magic(&np->saddr, &np->daddr, len, IPPROTO_TCP, 0); 952 th->check = ~csum_ipv6_magic(&np->saddr, &np->daddr, len, IPPROTO_TCP, 0);
953 skb->csum_start = skb_transport_header(skb) - skb->head;
953 skb->csum_offset = offsetof(struct tcphdr, check); 954 skb->csum_offset = offsetof(struct tcphdr, check);
954 } else { 955 } else {
955 th->check = csum_ipv6_magic(&np->saddr, &np->daddr, len, IPPROTO_TCP, 956 th->check = csum_ipv6_magic(&np->saddr, &np->daddr, len, IPPROTO_TCP,
@@ -972,6 +973,7 @@ static int tcp_v6_gso_send_check(struct sk_buff *skb)
972 th->check = 0; 973 th->check = 0;
973 th->check = ~csum_ipv6_magic(&ipv6h->saddr, &ipv6h->daddr, skb->len, 974 th->check = ~csum_ipv6_magic(&ipv6h->saddr, &ipv6h->daddr, skb->len,
974 IPPROTO_TCP, 0); 975 IPPROTO_TCP, 0);
976 skb->csum_start = skb_transport_header(skb) - skb->head;
975 skb->csum_offset = offsetof(struct tcphdr, check); 977 skb->csum_offset = offsetof(struct tcphdr, check);
976 skb->ip_summed = CHECKSUM_PARTIAL; 978 skb->ip_summed = CHECKSUM_PARTIAL;
977 return 0; 979 return 0;