Re: [PATCH] tcp: TCP_USER_TIMEOUT can not work in tcp_probe_timer()
From: Eric Dumazet <hidden>
Date: 2017-09-13 14:41:07
On Wed, 2017-09-13 at 15:15 +0800, liujian wrote:
在 2017/9/13 14:56, liujian 写道:quoted
在 2017/9/12 23:38, Eric Dumazet 写道:quoted
On Tue, 2017-09-12 at 08:05 -0700, Eric Dumazet wrote:quoted
On Tue, 2017-09-12 at 14:08 +0800, liujian wrote:quoted
Hi, In the scenario, tcp server side IP changed, and at that memont, userspace application still send data continuously; tcp_send_head(sk)'s timestamp always be refreshed. Here is the packetdrill script: 0 socket(..., SOCK_STREAM, IPPROTO_TCP) = 3 +0 setsockopt(3, SOL_SOCKET, SO_REUSEADDR, [1], 4) = 0 +0 bind(3, ..., ...) = 0 +0 listen(3, 1) = 0 +0 < S 0:0(0) win 0 <mss 1460,sackOK,nop,nop,nop,wscale 7> +0 > S. 0:0(0) ack 1 <mss 1460,nop,nop,sackOK,nop,wscale 7> +.1 < . 1:1(0) ack 1 win 65530 +0 accept(3, ..., ...) = 4 +0 setsockopt(4, SOL_TCP, TCP_USER_TIMEOUT, [3000], 4) = 0 +0 write(4, ..., 24) = 24 +0 > P. 1:25(24) ack 1 win 229 +.1 < . 1:1(0) ack 25 win 65530 //change the ipaddress +1 `ifconfig tun0 192.168.0.10/16` +1 write(4, ..., 24) = 24 +1 write(4, ..., 24) = 24 +1 write(4, ..., 24) = 24 +1 write(4, ..., 24) = 24 +3 write(4, ..., 24) = 24 +3 write(4, ..., 24) = 24 +3 write(4, ..., 24) = 24 +3 write(4, ..., 24) = 24 +3 write(4, ..., 24) = 24 +3 write(4, ..., 24) = 24 +3 write(4, ..., 24) = 24 +3 write(4, ..., 24) = 24 +3 write(4, ..., 24) = 24 +3 write(4, ..., 24) = 24 +3 write(4, ..., 24) = 24 +3 write(4, ..., 24) = 24 +3 write(4, ..., 24) = 24 +3 write(4, ..., 24) = 24 +3 write(4, ..., 24) = 24 +3 write(4, ..., 24) = 24 +3 write(4, ..., 24) = 24 +3 write(4, ..., 24) = 24 +3 write(4, ..., 24) = 24 +3 write(4, ..., 24) = 24 +3 write(4, ..., 24) = 24 +3 write(4, ..., 24) = 24 +0 `ifconfig tun0 192.168.0.1/16` +0 < . 1:1(0) ack 1 win 1000 +0 write(4, ..., 24) = -1This has nothing to do with the code patch you have changed. How have you tested your patch exactly ?I tested the patch, it can work. [root@localhost ~]# time ./gtests/net/packetdrill/packetdrill test.pkt test.pkt:24: runtime error in write call: Expected result 24 but got -1 with errno 110 (Connection timed out) real 0m5.356s user 0m0.026s sys 0m0.104s [root@localhost ~]# ss -toenmi src :8080 State Recv-Q Send-Q Local Address:Port Peer Address:Port ESTAB 0 48 192.168.0.1:8080 192.0.2.1:39559 timer:(persist,186ms,2) ino:37178 sk:6 <-> skmem:(r0,rb369280,t0,tb87040,f1792,w2304,o0,bl0) sack cubic wscale:7,7 rto:301 backoff:2 rtt:100.253/37.643 mss:1460 cwnd:10 bytes_acked:24 segs_out:5 segs_in:3 send 1.2Mbps lastsnd:976 lastrcv:4082 lastack:3982 pacing_rate 2.3Mbps rcv_space:29200 if change the TCP_USER_TIMEOUT to 30s, test result as below: [root@localhost ~]# time ./gtests/net/packetdrill/packetdrill test.pkt test.pkt:37: runtime error in write call: Expected result 24 but got -1 with errno 110 (Connection timed out) real 0m44.362s user 0m0.018s sys 0m0.110s ESTAB 0 360 192.168.0.1:8080 192.0.2.1:47577 timer:(persist,516ms,6) ino:18806 sk:5 <-> skmem:(r0,rb369280,t0,tb87040,f1792,w2304,o0,bl0) sack cubic wscale:7,7 rto:301 backoff:6 rtt:100.228/37.623 mss:10 bytes_acked:24 segs_out:22 segs_in:3 send 1.2Mbps lastsnd:2343 lastrcv:40450 lastack:40350 pacing_rate 2.3Mbps rcv_spquoted
lpaa23:~# ss -toenmi src :8080 State Recv-Q Send-Q Local Address:Port Peer Address:Port ESTAB 0 144 192.168.134.161:8080 192.0.2.1:51165 timer:(persist,8.262ms,5) ino:1 82083 sk:3 <-> skmem:(r0,rb359040,t0,tb46080,f1792,w2304,o0,bl0,d0) sack cubic wscale:7,8 rto:301 backoff:5 rtt:100.127/37.576 mss:1460 rcvmss:536 advmss:1460 cwnd:10 bytes_acked:24 segs_out:12 segs_in:3 data_segs_out:12 send 1.2Mbps lastsnd:1370 l astrcv:13348 lastack:13248 pacing_rate 2.3Mbps delivery_rate 116.7Kbps app_limited busy:11346ms rcv_space:29200 notsent:1 44 minrtt:100.043userspace application still send data continuously This is the typical RTO timer, not zero window probe.with the script, it is not zero window; but the code enter tcp_probe_timer. ->tcp_sendmsg -->tcp_push ---->__tcp_push_pending_frames ------>tcp_write_xmit -------->tcp_transmit_skb (at this function, tcp_send_head(sk)'s timestamp was be refreshed) ---------->ip_queue_xmit (can not find route, return -EHOSTUNREACH) -------->tcp_transmit_skb (send fail, do not advance send head) ------->tcp_check_probe_timer (reset ICSK_TIME_PROBE0 timer)sorry, change to ->tcp_sendmsg -->tcp_push ---->__tcp_push_pending_frames ------>tcp_write_xmit -------->tcp_transmit_skb (at this function, tcp_send_head(sk)'s timestamp was be refreshed) ---------->ip_queue_xmit (can not find route, return -EHOSTUNREACH) ------>tcp_write_xmit (send fail, do not advance send head) ------>tcp_check_probe_timer (reset ICSK_TIME_PROBE0 timer)
OK but : 1) keepalive_time_elapsed() returns jiffies, and you compare it to a ms value. It will break on kernels with HZ=100 2) keepalive_time_elapsed() is reset every time a packet is received. With following packetdrill your patch (even if we fix 1)) breaks again # ./packetdrill --local_ip 192.168.102.64 user_timeout.pkt # cat user_timeout.pkt 0 socket(..., SOCK_STREAM, IPPROTO_TCP) = 3 +0 setsockopt(3, SOL_SOCKET, SO_REUSEADDR, [1], 4) = 0 +0 bind(3, ..., ...) = 0 +0 listen(3, 1) = 0 +0 `ifconfig tun0 192.168.102.64/16; ip ro add 192.0.2.1 dev tun0` +0 < S 0:0(0) win 0 <mss 1460,sackOK,nop,nop,nop,wscale 7> +0 > S. 0:0(0) ack 1 <mss 1460,nop,nop,sackOK,nop,wscale 8> +.1 < . 1:1(0) ack 1 win 65530 +0 accept(3, ..., ...) = 4 +0 setsockopt(4, SOL_TCP, TCP_USER_TIMEOUT, [3000], 4) = 0 +0 write(4, ..., 24) = 24 +0 > P. 1:25(24) ack 1 win 115 +.1 < . 1:1(0) ack 25 win 65530 //change the ipaddress +1 `ifconfig tun0 192.168.0.10/16` +1 write(4, ..., 24) = 24 +1 write(4, ..., 24) = 24 +1 write(4, ..., 24) = 24 +1 write(4, ..., 24) = 24 +0 `ifconfig tun0 192.168.102.64/16` +0 < . 1:2(1) ack 25 win 65530 +0 `ifconfig tun0 192.168.0.10/16` +3 write(4, ..., 24) = 24 +3 write(4, ..., 24) = 24 +3 write(4, ..., 24) = 24 +3 write(4, ..., 24) = 24 +3 write(4, ..., 24) = 24 +3 write(4, ..., 24) = 24 +3 write(4, ..., 24) = 24 +3 write(4, ..., 24) = 24 +3 write(4, ..., 24) = 24 +3 write(4, ..., 24) = 24 +3 write(4, ..., 24) = 24 +3 write(4, ..., 24) = 24 +3 write(4, ..., 24) = 24 +3 write(4, ..., 24) = 24 +3 write(4, ..., 24) = 24 +3 write(4, ..., 24) = 24 +3 write(4, ..., 24) = 24 +3 write(4, ..., 24) = 24 +3 write(4, ..., 24) = 24 +3 write(4, ..., 24) = 24 +3 write(4, ..., 24) = 24 +3 write(4, ..., 24) = 24 +0 `ifconfig tun0 192.168.0.1/16` +0 < . 1:1(0) ack 1 win 1000 +0 write(4, ..., 24) = -1 I would instead try to keep a meaningful value in tcp_send_head(sk)->skb_mstamp if the transmit failed. Or more exactly change skb->skb_mstamp only on (successfully) transmitted skb. I will provide a patch ( fixing net/ipv4/tcp_output.c )