user/sven/linux.git/include/linux/snmp.h, branch v3.4.67

tcp: implement RFC 5961 4.2

2013-01-11T17:07:15Z

[ 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 Cc: Kiran Kumar Kella Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman

tcp: implement RFC 5961 3.2

2013-01-11T17:07:14Z

[ Upstream commit 282f23c6ee343126156dd41218b22ece96d747e3 ] Implement the RFC 5691 mitigation against Blind Reset attack using RST bit. Idea is to validate incoming RST sequence, to match RCV.NXT value, instead of previouly accepted window : (RCV.NXT <= SEG.SEQ < RCV.NXT+RCV.WND) If sequence is in window but not an exact match, send a "challenge ACK", so that the other part can resend an RST with the appropriate sequence. Add a new sysctl, tcp_challenge_ack_limit, to limit number of challenge ACK sent per second. Add a new SNMP counter to count number of challenge acks sent. (netstat -s | grep TCPChallengeACK) Signed-off-by: Eric Dumazet Cc: Kiran Kumar Kella Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman

tcp: reduce out_of_order memory use

2012-03-19T20:53:08Z

With increasing receive window sizes, but speed of light not improved that much, out of order queue can contain a huge number of skbs, waiting to be moved to receive_queue when missing packets can fill the holes. Some devices happen to use fat skbs (truesize of 4096 + sizeof(struct sk_buff)) to store regular (MTU <= 1500) frames. This makes highly probable sk_rmem_alloc hits sk_rcvbuf limit, which can be 4Mbytes in many cases. When limit is hit, tcp stack calls tcp_collapse_ofo_queue(), a true latency killer and cpu cache blower. Doing the coalescing attempt each time we add a frame in ofo queue permits to keep memory use tight and in many cases avoid the tcp_collapse() thing later. Tested on various wireless setups (b43, ath9k, ...) known to use big skb truesize, this patch removed the "packets collapsed in receive queue due to low socket buffer" I had before. This also reduced average memory used by tcp sockets. With help from Neal Cardwell. Signed-off-by: Eric Dumazet Cc: Neal Cardwell Cc: Yuchung Cheng Cc: H.K. Jerry Chu Cc: Tom Herbert Cc: Ilpo Järvinen Acked-by: Neal Cardwell Signed-off-by: David S. Miller

tcp: add LINUX_MIB_TCPRETRANSFAIL counter

2012-01-26T18:51:00Z

It might be useful to get a counter of failed tcp_retransmit_skb() calls. Reported-by: Satoru Moriya Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller

tcp: detect loss above high_seq in recovery

2012-01-22T20:08:44Z

Correctly implement a loss detection heuristic: New sequences (above high_seq) sent during the fast recovery are deemed lost when higher sequences are SACKed. Current code does not catch these losses, because tcp_mark_head_lost() does not check packets beyond high_seq. The fix is straight-forward by checking packets until the highest sacked packet. In addition, all the FLAG_DATA_LOST logic are in-effective and redundant and can be removed. Update the loss heuristic comments. The algorithm above is documented as heuristic B, but it is redundant too because heuristic A already covers B. Note that this change only marks some forward-retransmitted packets LOST. It does NOT forbid TCP performing further CWR on new losses. A potential follow-up patch under preparation is to perform another CWR on "new" losses such as 1) sequence above high_seq is lost (by resetting high_seq to snd_nxt) 2) retransmission is lost. Signed-off-by: Yuchung Cheng Signed-off-by: David S. Miller

tcp: Change possible SYN flooding messages

2011-09-15T18:49:43Z

"Possible SYN flooding on port xxxx " messages can fill logs on servers. Change logic to log the message only once per listener, and add two new SNMP counters to track : TCPReqQFullDoCookies : number of times a SYNCOOKIE was replied to client TCPReqQFullDrop : number of times a SYN request was dropped because syncookies were not enabled. Based on a prior patch from Tom Herbert, and suggestions from David. Signed-off-by: Eric Dumazet CC: Tom Herbert Signed-off-by: David S. Miller

tcp: Replace time wait bucket msg by counter

2010-12-08T20:16:33Z

Rather than printing the message to the log, use a mib counter to keep track of the count of occurences of time wait bucket overflow. Reduces spam in logs. Signed-off-by: Tom Herbert Signed-off-by: David S. Miller

ipv4: add LINUX_MIB_IPRPFILTER snmp counter

2010-06-03T10:18:19Z

Christoph Lameter mentioned that packets could be dropped in input path because of rp_filter settings, without any SNMP counter being incremented. System administrator can have a hard time to track the problem. This patch introduces a new counter, LINUX_MIB_IPRPFILTER, incremented each time we drop a packet because Reverse Path Filter triggers. (We receive an IPv4 datagram on a given interface, and find the route to send an answer would use another interface) netstat -s | grep IPReversePathFilter IPReversePathFilter: 21714 Reported-by: Christoph Lameter Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller

icmp: Account for ICMP out errors

2010-04-03T22:09:04Z

When ip_append() fails because of socket limit or memory shortage, increment ICMP_MIB_OUTERRORS counter, so that "netstat -s" can report these errors. LANG=C netstat -s | grep "ICMP messages failed" 0 ICMP messages failed For IPV6, implement ICMP6_MIB_OUTERRORS counter as well. # grep Icmp6OutErrors /proc/net/dev_snmp6/* /proc/net/dev_snmp6/eth0:Icmp6OutErrors 0 /proc/net/dev_snmp6/lo:Icmp6OutErrors 0 Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller

tcp: Add SNMP counter for DEFER_ACCEPT

2010-03-22T01:31:35Z

Its currently hard to diagnose when ACK frames are dropped because an application set TCP_DEFER_ACCEPT on its listening socket. See http://bugzilla.kernel.org/show_bug.cgi?id=15507 This patch adds a SNMP value, named TCPDeferAcceptDrop netstat -s | grep TCPDeferAcceptDrop TCPDeferAcceptDrop: 0 This counter is incremented every time we drop a pure ACK frame received by a socket in SYN_RECV state because its SYNACK retrans count is lower than defer_accept value. Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller