kernel/linux.git/include/net/tcp.h, branch v3.12.13

tcp: Change return value of tcp_rcv_established()

2013-09-04T04:27:28+00:00

tcp_rcv_established() returns only one value namely 0. We change the return value to void (as suggested by David Miller). After commit 0c24604b (tcp: implement RFC 5961 4.2), we no longer send RSTs in response to SYNs. We can remove the check and processing on the return value of tcp_rcv_established(). We also fix jtcp_rcv_established() in tcp_probe.c to match that of tcp_rcv_established(). Signed-off-by: Vijay Subramanian Signed-off-by: David S. Miller

tcp: TSO packets automatic sizing

2013-08-29T19:50:06+00:00

After hearing many people over past years complaining against TSO being bursty or even buggy, we are proud to present automatic sizing of TSO packets. One part of the problem is that tcp_tso_should_defer() uses an heuristic relying on upcoming ACKS instead of a timer, but more generally, having big TSO packets makes little sense for low rates, as it tends to create micro bursts on the network, and general consensus is to reduce the buffering amount. This patch introduces a per socket sk_pacing_rate, that approximates the current sending rate, and allows us to size the TSO packets so that we try to send one packet every ms. This field could be set by other transports. Patch has no impact for high speed flows, where having large TSO packets makes sense to reach line rate. For other flows, this helps better packet scheduling and ACK clocking. This patch increases performance of TCP flows in lossy environments. A new sysctl (tcp_min_tso_segs) is added, to specify the minimal size of a TSO packet (default being 2). A follow-up patch will provide a new packet scheduler (FQ), using sk_pacing_rate as an input to perform optional per flow pacing. This explains why we chose to set sk_pacing_rate to twice the current rate, allowing 'slow start' ramp up. sk_pacing_rate = 2 * cwnd * mss / srtt v2: Neal Cardwell reported a suspect deferring of last two segments on initial write of 10 MSS, I had to change tcp_tso_should_defer() to take into account tp->xmit_size_goal_segs Signed-off-by: Eric Dumazet Cc: Neal Cardwell Cc: Yuchung Cheng Cc: Van Jacobson Cc: Tom Herbert Acked-by: Yuchung Cheng Acked-by: Neal Cardwell Signed-off-by: David S. Miller

net: syncookies: export cookie_v6_init_sequence/cookie_v6_check

2013-08-27T22:28:04+00:00

Extract the local TCP stack independant parts of tcp_v6_init_sequence() and cookie_v6_check() and export them for use by the upcoming IPv6 SYNPROXY target. Signed-off-by: Patrick McHardy Acked-by: David S. Miller Tested-by: Martin Topholm Signed-off-by: Jesper Dangaard Brouer Signed-off-by: Pablo Neira Ayuso

net: syncookies: export cookie_v4_init_sequence/cookie_v4_check

2013-08-27T22:27:44+00:00

Extract the local TCP stack independant parts of tcp_v4_init_sequence() and cookie_v4_check() and export them for use by the upcoming SYNPROXY target. Signed-off-by: Patrick McHardy Acked-by: David S. Miller Tested-by: Martin Topholm Signed-off-by: Jesper Dangaard Brouer Signed-off-by: Pablo Neira Ayuso

tcp: add server ip to encrypt cookie in fast open

2013-08-10T07:35:33+00:00

Encrypt the cookie with both server and client IPv4 addresses, such that multi-homed server will grant different cookies based on both the source and destination IPs. No client change is needed since cookie is opaque to the client. Signed-off-by: Yuchung Cheng Reviewed-by: Eric Dumazet Acked-by: Neal Cardwell Signed-off-by: David S. Miller

tcp: Remove unused tcpct declarations and comments

2013-07-31T19:16:45+00:00

Remove declaration, 4 defines and confusing comment that are no longer used since 1a2c6181c4 ("tcp: Remove TCPCT"). Signed-off-by: Dmitry Popov Acked-by: Christoph Paasch Signed-off-by: David S. Miller

tcp: TCP_NOTSENT_LOWAT socket option

2013-07-25T00:54:48+00:00

Idea of this patch is to add optional limitation of number of unsent bytes in TCP sockets, to reduce usage of kernel memory. TCP receiver might announce a big window, and TCP sender autotuning might allow a large amount of bytes in write queue, but this has little performance impact if a large part of this buffering is wasted : Write queue needs to be large only to deal with large BDP, not necessarily to cope with scheduling delays (incoming ACKS make room for the application to queue more bytes) For most workloads, using a value of 128 KB or less is OK to give applications enough time to react to POLLOUT events in time (or being awaken in a blocking sendmsg()) This patch adds two ways to set the limit : 1) Per socket option TCP_NOTSENT_LOWAT 2) A sysctl (/proc/sys/net/ipv4/tcp_notsent_lowat) for sockets not using TCP_NOTSENT_LOWAT socket option (or setting a zero value) Default value being UINT_MAX (0xFFFFFFFF), meaning this has no effect. This changes poll()/select()/epoll() to report POLLOUT only if number of unsent bytes is below tp->nosent_lowat Note this might increase number of sendmsg()/sendfile() calls when using non blocking sockets, and increase number of context switches for blocking sockets. Note this is not related to SO_SNDLOWAT (as SO_SNDLOWAT is defined as : Specify the minimum number of bytes in the buffer until the socket layer will pass the data to the protocol) Tested: netperf sessions, and watching /proc/net/protocols "memory" column for TCP With 200 concurrent netperf -t TCP_STREAM sessions, amount of kernel memory used by TCP buffers shrinks by ~55 % (20567 pages instead of 45458) lpq83:~# echo -1 >/proc/sys/net/ipv4/tcp_notsent_lowat lpq83:~# (super_netperf 200 -t TCP_STREAM -H remote -l 90 &); sleep 60 ; grep TCP /proc/net/protocols TCPv6 1880 2 45458 no 208 yes ipv6 y y y y y y y y y y y y y n y y y y y TCP 1696 508 45458 no 208 yes kernel y y y y y y y y y y y y y n y y y y y lpq83:~# echo 131072 >/proc/sys/net/ipv4/tcp_notsent_lowat lpq83:~# (super_netperf 200 -t TCP_STREAM -H remote -l 90 &); sleep 60 ; grep TCP /proc/net/protocols TCPv6 1880 2 20567 no 208 yes ipv6 y y y y y y y y y y y y y n y y y y y TCP 1696 508 20567 no 208 yes kernel y y y y y y y y y y y y y n y y y y y Using 128KB has no bad effect on the throughput or cpu usage of a single flow, although there is an increase of context switches. A bonus is that we hold socket lock for a shorter amount of time and should improve latencies of ACK processing. lpq83:~# echo -1 >/proc/sys/net/ipv4/tcp_notsent_lowat lpq83:~# perf stat -e context-switches ./netperf -H 7.7.7.84 -t omni -l 20 -c -i10,3 OMNI Send TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to 7.7.7.84 () port 0 AF_INET : +/-2.500% @ 99% conf. Local Remote Local Elapsed Throughput Throughput Local Local Remote Remote Local Remote Service Send Socket Recv Socket Send Time Units CPU CPU CPU CPU Service Service Demand Size Size Size (sec) Util Util Util Util Demand Demand Units Final Final % Method % Method 1651584 6291456 16384 20.00 17447.90 10^6bits/s 3.13 S -1.00 U 0.353 -1.000 usec/KB Performance counter stats for './netperf -H 7.7.7.84 -t omni -l 20 -c -i10,3': 412,514 context-switches 200.034645535 seconds time elapsed lpq83:~# echo 131072 >/proc/sys/net/ipv4/tcp_notsent_lowat lpq83:~# perf stat -e context-switches ./netperf -H 7.7.7.84 -t omni -l 20 -c -i10,3 OMNI Send TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to 7.7.7.84 () port 0 AF_INET : +/-2.500% @ 99% conf. Local Remote Local Elapsed Throughput Throughput Local Local Remote Remote Local Remote Service Send Socket Recv Socket Send Time Units CPU CPU CPU CPU Service Service Demand Size Size Size (sec) Util Util Util Util Demand Demand Units Final Final % Method % Method 1593240 6291456 16384 20.00 17321.16 10^6bits/s 3.35 S -1.00 U 0.381 -1.000 usec/KB Performance counter stats for './netperf -H 7.7.7.84 -t omni -l 20 -c -i10,3': 2,675,818 context-switches 200.029651391 seconds time elapsed Signed-off-by: Eric Dumazet Cc: Neal Cardwell Cc: Yuchung Cheng Acked-By: Yuchung Cheng Signed-off-by: David S. Miller

tcp: prefer packet timing to TS-ECR for RTT

2013-07-23T00:53:42+00:00

Prefer packet timings to TS-ecr for RTT measurements when both sources are available. That's because broken middle-boxes and remote peer can return packets with corrupted TS ECR fields. Similarly most congestion controls that require RTT signals favor timing-based sources as well. Also check for bad TS ECR values to avoid RTT blow-ups. It has happened on production Web servers. Signed-off-by: Yuchung Cheng Acked-by: Neal Cardwell Signed-off-by: David S. Miller

tcp: consolidate SYNACK RTT sampling

2013-07-23T00:53:42+00:00

The first patch consolidates SYNACK and other RTT measurement to use a central function tcp_ack_update_rtt(). A (small) bonus is now SYNACK RTT measurement happens after PAWS check, potentially reducing the impact of RTO seeding on bad TCP timestamps values. Signed-off-by: Yuchung Cheng Signed-off-by: David S. Miller

tcp: remove invalid __rcu annotation

2013-06-25T09:44:05+00:00

struct tcp_fastopen_context has a field named tfm, which is a pointer to a crypto_cipher structure. It currently has a __rcu annotation, which is not needed at all. tcp_fastopen_ctx is the pointer fetched by rcu_dereference(), but once we have a pointer to current tcp_fastopen_context, we do not use/need rcu_dereference() to access tfm. This fixes a lot of sparse errors like the following : net/ipv4/tcp_fastopen.c:21:31: warning: incorrect type in argument 1 (different address spaces) net/ipv4/tcp_fastopen.c:21:31: expected struct crypto_cipher *tfm net/ipv4/tcp_fastopen.c:21:31: got struct crypto_cipher [noderef] *tfm Signed-off-by: Eric Dumazet Cc: Jerry Chu Signed-off-by: David S. Miller