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| author | Eric Dumazet <edumazet@google.com> | 2012-07-17 01:41:30 +0000 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2013-01-11 09:03:48 -0800 |
| commit | ab5c718d0fd643ba6f2112235e12ea5222f4edf3 (patch) | |
| tree | 02a32971cc7cc44623e78292bf54b2056268dbf3 /net/ipv4/tcp_input.c | |
| parent | 86791bbfe5ed7b275be040cfeff049a1624af1b7 (diff) | |
| download | kernel_samsung_smdk4412-ab5c718d0fd643ba6f2112235e12ea5222f4edf3.zip kernel_samsung_smdk4412-ab5c718d0fd643ba6f2112235e12ea5222f4edf3.tar.gz kernel_samsung_smdk4412-ab5c718d0fd643ba6f2112235e12ea5222f4edf3.tar.bz2 | |
tcp: implement RFC 5961 4.2
[ Upstream commit 0c24604b68fc7810d429d6c3657b6f148270e528 ]
Implement the RFC 5691 mitigation against Blind
Reset attack using SYN bit.
Section 4.2 of RFC 5961 advises to send a Challenge ACK and drop
incoming packet, instead of resetting the session.
Add a new SNMP counter to count number of challenge acks sent
in response to SYN packets.
(netstat -s | grep TCPSYNChallenge)
Remove obsolete TCPAbortOnSyn, since we no longer abort a TCP session
because of a SYN flag.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Kiran Kumar Kella <kkiran@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'net/ipv4/tcp_input.c')
| -rw-r--r-- | net/ipv4/tcp_input.c | 32 |
1 files changed, 15 insertions, 17 deletions
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index 04ef087..bf79a5a 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -5188,8 +5188,8 @@ static void tcp_send_challenge_ack(struct sock *sk) /* Does PAWS and seqno based validation of an incoming segment, flags will * play significant role here. */ -static int tcp_validate_incoming(struct sock *sk, struct sk_buff *skb, - struct tcphdr *th, int syn_inerr) +static bool tcp_validate_incoming(struct sock *sk, struct sk_buff *skb, + struct tcphdr *th, int syn_inerr) { u8 *hash_location; struct tcp_sock *tp = tcp_sk(sk); @@ -5241,20 +5241,22 @@ static int tcp_validate_incoming(struct sock *sk, struct sk_buff *skb, /* step 3: check security and precedence [ignored] */ - /* step 4: Check for a SYN in window. */ - if (th->syn && !before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) { + /* step 4: Check for a SYN + * RFC 5691 4.2 : Send a challenge ack + */ + if (th->syn) { if (syn_inerr) TCP_INC_STATS_BH(sock_net(sk), TCP_MIB_INERRS); - NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPABORTONSYN); - tcp_reset(sk); - return -1; + NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPSYNCHALLENGE); + tcp_send_challenge_ack(sk); + goto discard; } - return 1; + return true; discard: __kfree_skb(skb); - return 0; + return false; } /* @@ -5284,7 +5286,6 @@ int tcp_rcv_established(struct sock *sk, struct sk_buff *skb, struct tcphdr *th, unsigned len) { struct tcp_sock *tp = tcp_sk(sk); - int res; /* * Header prediction. @@ -5464,9 +5465,8 @@ slow_path: * Standard slow path. */ - res = tcp_validate_incoming(sk, skb, th, 1); - if (res <= 0) - return -res; + if (!tcp_validate_incoming(sk, skb, th, 1)) + return 0; step5: if (th->ack && tcp_ack(sk, skb, FLAG_SLOWPATH) < 0) @@ -5776,7 +5776,6 @@ int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb, struct tcp_sock *tp = tcp_sk(sk); struct inet_connection_sock *icsk = inet_csk(sk); int queued = 0; - int res; tp->rx_opt.saw_tstamp = 0; @@ -5831,9 +5830,8 @@ int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb, return 0; } - res = tcp_validate_incoming(sk, skb, th, 0); - if (res <= 0) - return -res; + if (!tcp_validate_incoming(sk, skb, th, 0)) + return 0; /* step 5: check the ACK field */ if (th->ack) { |