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authorEric Dumazet <eric.dumazet@gmail.com>2010-09-20 20:16:27 +0000
committerDavid S. Miller <davem@davemloft.net>2010-09-24 14:41:04 -0700
commit59104f062435c7816e39ee5ed504a69cb8037f10 (patch)
treecc77c6202d01b9c152634b836fa06e77b27d14fc /net/ipv4/ip_output.c
parenta02cec2155fbea457eca8881870fd2de1a4c4c76 (diff)
ip: take care of last fragment in ip_append_data
While investigating a bit, I found ip_fragment() slow path was taken because ip_append_data() provides following layout for a send(MTU + N*(MTU - 20)) syscall : - one skb with 1500 (mtu) bytes - N fragments of 1480 (mtu-20) bytes (before adding IP header) last fragment gets 17 bytes of trail data because of following bit: if (datalen == length + fraggap) alloclen += rt->dst.trailer_len; Then esp4 adds 16 bytes of data (while trailer_len is 17... hmm... another bug ?) In ip_fragment(), we notice last fragment is too big (1496 + 20) > mtu, so we take slow path, building another skb chain. In order to avoid taking slow path, we should correct ip_append_data() to make sure last fragment has real trail space, under mtu... Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/ipv4/ip_output.c')
-rw-r--r--net/ipv4/ip_output.c9
1 files changed, 6 insertions, 3 deletions
diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c
index e42762023c27..3551b6dc7419 100644
--- a/net/ipv4/ip_output.c
+++ b/net/ipv4/ip_output.c
@@ -926,16 +926,19 @@ alloc_new_skb:
!(rt->dst.dev->features&NETIF_F_SG))
alloclen = mtu;
else
- alloclen = datalen + fragheaderlen;
+ alloclen = fraglen;
/* The last fragment gets additional space at tail.
* Note, with MSG_MORE we overallocate on fragments,
* because we have no idea what fragment will be
* the last.
*/
- if (datalen == length + fraggap)
+ if (datalen == length + fraggap) {
alloclen += rt->dst.trailer_len;
-
+ /* make sure mtu is not reached */
+ if (datalen > mtu - fragheaderlen - rt->dst.trailer_len)
+ datalen -= ALIGN(rt->dst.trailer_len, 8);
+ }
if (transhdrlen) {
skb = sock_alloc_send_skb(sk,
alloclen + hh_len + 15,