tcp: implement RFC 5961 4.2
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>
diff --git a/include/linux/snmp.h b/include/linux/snmp.h
index 673e0e9..e5fcbd0 100644
--- a/include/linux/snmp.h
+++ b/include/linux/snmp.h
@@ -208,7 +208,6 @@
LINUX_MIB_TCPDSACKOFOSENT, /* TCPDSACKOfoSent */
LINUX_MIB_TCPDSACKRECV, /* TCPDSACKRecv */
LINUX_MIB_TCPDSACKOFORECV, /* TCPDSACKOfoRecv */
- LINUX_MIB_TCPABORTONSYN, /* TCPAbortOnSyn */
LINUX_MIB_TCPABORTONDATA, /* TCPAbortOnData */
LINUX_MIB_TCPABORTONCLOSE, /* TCPAbortOnClose */
LINUX_MIB_TCPABORTONMEMORY, /* TCPAbortOnMemory */
@@ -238,6 +237,7 @@
LINUX_MIB_TCPOFODROP, /* TCPOFODrop */
LINUX_MIB_TCPOFOMERGE, /* TCPOFOMerge */
LINUX_MIB_TCPCHALLENGEACK, /* TCPChallengeACK */
+ LINUX_MIB_TCPSYNCHALLENGE, /* TCPSYNChallenge */
__LINUX_MIB_MAX
};