From c074da2810c118b3812f32d6754bd9ead2f169e7 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Tue, 26 Jun 2012 23:14:15 +0000 Subject: [PATCH] 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 Cc: Hans Schillstrom Signed-off-by: David S. Miller --- include/net/protocol.h | 2 +- include/net/route.h | 8 ++++---- include/net/tcp.h | 2 +- net/ipv4/arp.c | 2 +- net/ipv4/ip_fragment.c | 2 +- net/ipv4/ip_input.c | 5 +++-- net/ipv4/route.c | 8 +++++--- net/ipv4/tcp_ipv4.c | 4 +++- net/ipv4/xfrm4_input.c | 2 +- 9 files changed, 20 insertions(+), 15 deletions(-) diff --git a/include/net/protocol.h b/include/net/protocol.h index 967b926cbfb1f..7cfc8f76914d4 100644 --- a/include/net/protocol.h +++ b/include/net/protocol.h @@ -37,7 +37,7 @@ /* This is used to register protocols. */ struct net_protocol { - int (*early_demux)(struct sk_buff *skb); + int (*early_demux)(struct sk_buff *skb, bool *nocache); int (*handler)(struct sk_buff *skb); void (*err_handler)(struct sk_buff *skb, u32 info); int (*gso_send_check)(struct sk_buff *skb); diff --git a/include/net/route.h b/include/net/route.h index 47eb25ac1f7f8..6361f9335774c 100644 --- a/include/net/route.h +++ b/include/net/route.h @@ -201,18 +201,18 @@ static inline struct rtable *ip_route_output_gre(struct net *net, struct flowi4 } extern int ip_route_input_common(struct sk_buff *skb, __be32 dst, __be32 src, - u8 tos, struct net_device *devin, bool noref); + u8 tos, struct net_device *devin, bool noref, bool nocache); static inline int ip_route_input(struct sk_buff *skb, __be32 dst, __be32 src, u8 tos, struct net_device *devin) { - return ip_route_input_common(skb, dst, src, tos, devin, false); + return ip_route_input_common(skb, dst, src, tos, devin, false, false); } static inline int ip_route_input_noref(struct sk_buff *skb, __be32 dst, __be32 src, - u8 tos, struct net_device *devin) + u8 tos, struct net_device *devin, bool nocache) { - return ip_route_input_common(skb, dst, src, tos, devin, true); + return ip_route_input_common(skb, dst, src, tos, devin, true, nocache); } extern void ipv4_update_pmtu(struct sk_buff *skb, struct net *net, u32 mtu, diff --git a/include/net/tcp.h b/include/net/tcp.h index 6660ffc4963df..917ed2e55e8cf 100644 --- a/include/net/tcp.h +++ b/include/net/tcp.h @@ -325,7 +325,7 @@ extern void tcp_v4_err(struct sk_buff *skb, u32); extern void tcp_shutdown (struct sock *sk, int how); -extern int tcp_v4_early_demux(struct sk_buff *skb); +extern int tcp_v4_early_demux(struct sk_buff *skb, bool *nocache); extern int tcp_v4_rcv(struct sk_buff *skb); extern struct inet_peer *tcp_v4_get_peer(struct sock *sk); diff --git a/net/ipv4/arp.c b/net/ipv4/arp.c index 2e560f0c757df..6a97959443690 100644 --- a/net/ipv4/arp.c +++ b/net/ipv4/arp.c @@ -828,7 +828,7 @@ static int arp_process(struct sk_buff *skb) } if (arp->ar_op == htons(ARPOP_REQUEST) && - ip_route_input_noref(skb, tip, sip, 0, dev) == 0) { + ip_route_input_noref(skb, tip, sip, 0, dev, false) == 0) { rt = skb_rtable(skb); addr_type = rt->rt_type; diff --git a/net/ipv4/ip_fragment.c b/net/ipv4/ip_fragment.c index 8d07c973409ca..978d55f256eac 100644 --- a/net/ipv4/ip_fragment.c +++ b/net/ipv4/ip_fragment.c @@ -259,7 +259,7 @@ static void ip_expire(unsigned long arg) skb_dst_drop(head); iph = ip_hdr(head); err = ip_route_input_noref(head, iph->daddr, iph->saddr, - iph->tos, head->dev); + iph->tos, head->dev, false); if (err) goto out_rcu_unlock; diff --git a/net/ipv4/ip_input.c b/net/ipv4/ip_input.c index 2a39204de5bc0..7be54c8dcbe22 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) rcu_read_lock(); ipprot = rcu_dereference(inet_protos[protocol]); if (ipprot && ipprot->early_demux) - err = ipprot->early_demux(skb); + err = ipprot->early_demux(skb, &nocache); rcu_read_unlock(); } 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) NET_INC_STATS_BH(dev_net(skb->dev), diff --git a/net/ipv4/route.c b/net/ipv4/route.c index 81533e3a23d12..fdc7900f9d7a0 100644 --- a/net/ipv4/route.c +++ b/net/ipv4/route.c @@ -2214,7 +2214,7 @@ static int ip_mkroute_input(struct sk_buff *skb, */ static int ip_route_input_slow(struct sk_buff *skb, __be32 daddr, __be32 saddr, - u8 tos, struct net_device *dev) + u8 tos, struct net_device *dev, bool nocache) { struct fib_result res; struct in_device *in_dev = __in_dev_get_rcu(dev); @@ -2353,6 +2353,8 @@ local_input: rth->dst.error= -err; rth->rt_flags &= ~RTCF_LOCAL; } + if (nocache) + rth->dst.flags |= DST_NOCACHE; hash = rt_hash(daddr, saddr, fl4.flowi4_iif, rt_genid(net)); rth = rt_intern_hash(hash, rth, skb, fl4.flowi4_iif); err = 0; @@ -2395,7 +2397,7 @@ martian_source_keep_err: } int ip_route_input_common(struct sk_buff *skb, __be32 daddr, __be32 saddr, - u8 tos, struct net_device *dev, bool noref) + u8 tos, struct net_device *dev, bool noref, bool nocache) { struct rtable *rth; unsigned int hash; @@ -2471,7 +2473,7 @@ skip_cache: rcu_read_unlock(); return -EINVAL; } - res = ip_route_input_slow(skb, daddr, saddr, tos, dev); + res = ip_route_input_slow(skb, daddr, saddr, tos, dev, nocache); rcu_read_unlock(); return res; } diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c index 1781dc650b9d3..33aabd4fc20fa 100644 --- a/net/ipv4/tcp_ipv4.c +++ b/net/ipv4/tcp_ipv4.c @@ -1673,7 +1673,7 @@ csum_err: } EXPORT_SYMBOL(tcp_v4_do_rcv); -int tcp_v4_early_demux(struct sk_buff *skb) +int tcp_v4_early_demux(struct sk_buff *skb, bool *no_dst_cache) { struct net *net = dev_net(skb->dev); const struct iphdr *iph; @@ -1719,6 +1719,8 @@ int tcp_v4_early_demux(struct sk_buff *skb) } } } + } else { + *no_dst_cache = true; } out_err: diff --git a/net/ipv4/xfrm4_input.c b/net/ipv4/xfrm4_input.c index 06814b6216dc1..eee636b191b9c 100644 --- a/net/ipv4/xfrm4_input.c +++ b/net/ipv4/xfrm4_input.c @@ -28,7 +28,7 @@ static inline int xfrm4_rcv_encap_finish(struct sk_buff *skb) const struct iphdr *iph = ip_hdr(skb); if (ip_route_input_noref(skb, iph->daddr, iph->saddr, - iph->tos, skb->dev)) + iph->tos, skb->dev, false)) goto drop; } return dst_input(skb); -- 2.30.2