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authorEric Dumazet <edumazet@google.com>2012-06-26 23:14:15 +0000
committerDavid S. Miller <davem@davemloft.net>2012-06-27 15:34:24 -0700
commitc074da2810c118b3812f32d6754bd9ead2f169e7 (patch)
tree772c7fbb9da464f9afd6d56e9e610157ed665e8f /init
parent93040ae5cc8dcc893eca4a4366dc8415af278edf (diff)
downloadlinux-c074da2810c118b3812f32d6754bd9ead2f169e7.tar.bz2
ipv4: tcp: dont cache unconfirmed intput dst
DDOS synflood attacks hit badly IP route cache. On typical machines, this cache is allowed to hold up to 8 Millions dst entries, 256 bytes for each, for a total of 2GB of memory. rt_garbage_collect() triggers and tries to cleanup things. Eventually route cache is disabled but machine is under fire and might OOM and crash. This patch exploits the new TCP early demux, to set a nocache boolean in case incoming TCP frame is for a not yet ESTABLISHED or TIMEWAIT socket. This 'nocache' boolean is then used in case dst entry is not found in route cache, to create an unhashed dst entry (DST_NOCACHE) SYN-cookie-ACK sent use a similar mechanism (ipv4: tcp: dont cache output dst for syncookies), so after this patch, a machine is able to absorb a DDOS synflood attack without polluting its IP route cache. Signed-off-by: Eric Dumazet <edumazet@google.com> Cc: Hans Schillstrom <hans.schillstrom@ericsson.com> Signed-off-by: David S. Miller <davem@davemloft.net>
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