path: root/net/ipv4/ip_input.c
diff options
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 /net/ipv4/ip_input.c
parentbe2net: Fix to trim skb for padded vlan packets to workaround an ASIC Bug (diff)
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>
Diffstat (limited to '')
1 files changed, 3 insertions, 2 deletions
diff --git a/net/ipv4/ip_input.c b/net/ipv4/ip_input.c
index 2a39204de5bc..7be54c8dcbe2 100644
--- a/net/ipv4/ip_input.c
+++ b/net/ipv4/ip_input.c
@@ -326,6 +326,7 @@ static int ip_rcv_finish(struct sk_buff *skb)
if (skb_dst(skb) == NULL) {
int err = -ENOENT;
+ bool nocache = false;
if (sysctl_ip_early_demux) {
const struct net_protocol *ipprot;
@@ -334,13 +335,13 @@ static int ip_rcv_finish(struct sk_buff *skb)
ipprot = rcu_dereference(inet_protos[protocol]);
if (ipprot && ipprot->early_demux)
- err = ipprot->early_demux(skb);
+ err = ipprot->early_demux(skb, &nocache);
if (err) {
err = ip_route_input_noref(skb, iph->daddr, iph->saddr,
- iph->tos, skb->dev);
+ iph->tos, skb->dev, nocache);
if (unlikely(err)) {
if (err == -EXDEV)