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| author | Eric Dumazet <edumazet@google.com> | 2012-05-18 11:02:15 +0000 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2012-05-18 23:49:33 -0400 |
| commit | 72e843bb09d4533208aa5573861a983c46914019 (patch) | |
| tree | 989fec0c30d80aef7e036c01aa12c24977f50488 /net/ipv6/ip6_output.c | |
| parent | 6fba180ee8b1c86b03d33013b4c2fc54fc5fc248 (diff) | |
| download | lwn-72e843bb09d4533208aa5573861a983c46914019.tar.gz lwn-72e843bb09d4533208aa5573861a983c46914019.zip | |
ipv6: ip6_fragment() should check CHECKSUM_PARTIAL
Quoting Tore Anderson from :
If the allfrag feature has been set on a host route (due to an ICMPv6
Packet Too Big received indicating a MTU of less than 1280),
TCP SYN/ACK packets to that destination appears to get an incorrect
TCP checksum. This in turn means they are thrown away as invalid.
In the case of an IPv4 client behind a link with a MTU of less than
1260, accessing an IPv6 server through a stateless translator,
this means that the client can only download a single large file
from the server, because once it is in the server's routing cache
with the allfrag feature set, new TCP connections can no longer
be established.
</endquote>
It appears ip6_fragment() doesn't handle CHECKSUM_PARTIAL properly.
As network drivers are not prepared to fetch correct transport header, a
safe fix is to call skb_checksum_help() before fragmenting packet.
Reported-by: Tore Anderson <tore@fud.no>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Tested-by: Tore Anderson <tore@fud.no>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/ipv6/ip6_output.c')
| -rw-r--r-- | net/ipv6/ip6_output.c | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c index a254e4b5d968..3dc633f39372 100644 --- a/net/ipv6/ip6_output.c +++ b/net/ipv6/ip6_output.c @@ -788,6 +788,10 @@ slow_path_clean: } slow_path: + if ((skb->ip_summed == CHECKSUM_PARTIAL) && + skb_checksum_help(skb)) + goto fail; + left = skb->len - hlen; /* Space per frame */ ptr = hlen; /* Where to start from */ |