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| author |   Eric Dumazet <eric.dumazet@gmail.com> | 2010-09-20 20:16:27 +0000 |
|---|---|---|
| committer |   David S. Miller <davem@davemloft.net> | 2010-09-24 14:41:04 -0700 |
| commit | 59104f062435c7816e39ee5ed504a69cb8037f10 (patch) | |
| tree | cc77c6202d01b9c152634b836fa06e77b27d14fc /net/ipv4/ip_output.c | |
| parent | net: return operator cleanup (diff) | |
| download | linux-dev-59104f062435c7816e39ee5ed504a69cb8037f10.tar.xz linux-dev-59104f062435c7816e39ee5ed504a69cb8037f10.zip | |
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.c | 9 |
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, |