Hello,

We have a server application running which has a LISTEN on port 8115 and waits with the poll(2) syscall for incoming client connections:

Code:
# LANG=C netstat -an | fgrep 8115
tcp        0      0 0.0.0.0:8115            0.0.0.0:*               LISTEN      
tcp        0      0 10.146.200.41:8115      10.146.202.252:1106     ESTABLISHED 
tcp        0      0 10.146.200.41:8115      10.146.202.19:62295     ESTABLISHED 
tcp        0      0 10.146.200.41:8115      10.146.201.54:63310     ESTABLISHED
...

From time to time it happens that the TCP connection is established fine and the client is sending already data, as you can see in the TCPDUMP:

Code:
# tcpdump -n -S -r 8115.tcp.02 | fgrep 10.146.201.54.59273
reading from file 8115.tcp.02, link-type EN10MB (Ethernet)
09:18:39.694636 IP 10.146.201.54.59273 > 10.146.200.41.8115: S 3430710974:3430710974(0) win 8192 <mss 1452,nop,wscale 2,nop,n
op,sackOK>
09:18:39.694649 IP 10.146.200.41.8115 > 10.146.201.54.59273: S 2986597784:2986597784(0) ack 3430710975 win 14600 <mss 1460,no
p,nop,sackOK,nop,wscale 7>
09:18:39.750540 IP 10.146.201.54.59273 > 10.146.200.41.8115: . ack 2986597785 win 16698
09:18:39.751543 IP 10.146.201.54.59273 > 10.146.200.41.8115: P 3430710975:3430711016(41) ack 2986597785 win 16698
09:18:40.055344 IP 10.146.201.54.59273 > 10.146.200.41.8115: P 3430710975:3430711016(41) ack 2986597785 win 16698
09:18:40.655377 IP 10.146.201.54.59273 > 10.146.200.41.8115: P 3430710975:3430711016(41) ack 2986597785 win 16698
09:18:41.855471 IP 10.146.201.54.59273 > 10.146.200.41.8115: P 3430710975:3430711016(41) ack 2986597785 win 16698
09:18:41.855496 IP 10.146.200.41.8115 > 10.146.201.54.59273: . ack 3430711016 win 115
09:18:42.715302 IP 10.146.200.41.8115 > 10.146.201.54.59273: P 2986597785:2986597799(14) ack 3430711016 win 115
09:18:42.757938 IP 10.146.201.54.59273 > 10.146.200.41.8115: P 3430711016:3430711036(20) ack 2986597799 win 16694
09:18:42.758026 IP 10.146.200.41.8115 > 10.146.201.54.59273: . ack 3430711036 win 115
09:18:42.766887 IP 10.146.200.41.8115 > 10.146.201.54.59273: P 2986597799:2986597914(115) ack 3430711036 win 115
09:18:43.035501 IP 10.146.201.54.59273 > 10.146.200.41.8115: . ack 2986597914 win 16665
...

but the server needs seconds more to be waked up in its poll():

Code:
13455 08:25:59.162706 poll([{fd=3, events=POLLIN|POLLPRI}, {fd=-1}], 2, 4294967295 <unfinished ...>
13455 09:18:41.613083 <... poll resumed> ) = 1 ([{fd=3, revents=POLLIN}]) <3162.450367>
13455 09:18:41.613250 --- SIGCHLD (Child exited) @ 0 (0) ---
13455 09:18:41.613789 waitpid(-1,  <unfinished ...>
13455 09:18:41.613853 <... waitpid resumed> [{WIFEXITED(s) && WEXITSTATUS(s) == 0}], WNOHANG) = 13491 <0.000057>
13455 09:18:41.613950 gettimeofday( <unfinished ...>
13455 09:18:41.613970 <... gettimeofday resumed> {1458029921, 613958}, NULL) = 0 <0.000013>
13455 09:18:41.613992 stat64("/etc/localtime",  <unfinished ...>
13455 09:18:41.614015 <... stat64 resumed> {st_mode=S_IFREG|0644, st_size=2335, ...}) = 0 <0.000013>
13455 09:18:41.614060 write(1, "15.03.2016 09:18:41.613  Sip2Sln"..., 97 <unfinished ...>
13455 09:18:41.614148 <... write resumed> ) = 97 <0.000060>
13455 09:18:41.614172 waitpid(-1,  <unfinished ...>
13455 09:18:41.614240 <... waitpid resumed> [{WIFEXITED(s) && WEXITSTATUS(s) == 0}], WNOHANG) = 13501 <0.000053>
13455 09:18:41.614293 gettimeofday( <unfinished ...>
13455 09:18:41.614334 <... gettimeofday resumed> {1458029921, 614327}, NULL) = 0 <0.000029>
13455 09:18:41.614365 stat64("/etc/localtime", {st_mode=S_IFREG|0644, st_size=2335, ...}) = 0 <0.000012>
13455 09:18:41.614439 write(1, "15.03.2016 09:18:41.614  Sip2Sln"..., 97) = 97 <0.000012>
13455 09:18:41.614486 waitpid(-1, [{WIFEXITED(s) && WEXITSTATUS(s) == 0}], WNOHANG) = 13515 <0.000027>
13455 09:18:41.614547 gettimeofday({1458029921, 614563}, NULL) = 0 <0.000009>
13455 09:18:41.614592 stat64("/etc/localtime", {st_mode=S_IFREG|0644, st_size=2335, ...}) = 0 <0.000010>
13455 09:18:41.614657 write(1, "15.03.2016 09:18:41.614  Sip2Sln"..., 97) = 97 <0.000011>
13455 09:18:41.614703 waitpid(-1, [{WIFEXITED(s) && WEXITSTATUS(s) == 0}], WNOHANG) = 13524 <0.000024>
13455 09:18:41.614881 gettimeofday( <unfinished ...>
13455 09:18:41.614913 <... gettimeofday resumed> {1458029921, 614898}, NULL) = 0 <0.000020>
13455 09:18:41.614960 stat64("/etc/localtime", {st_mode=S_IFREG|0644, st_size=2335, ...}) = 0 <0.000013>
13455 09:18:41.615505 write(1, "15.03.2016 09:18:41.614  Sip2Sln"..., 97 <unfinished ...>
13455 09:18:41.615982 <... write resumed> ) = 97 <0.000468>
13455 09:18:41.616064 waitpid(-1,  <unfinished ...>
13455 09:18:41.616097 <... waitpid resumed> 0xff81e938, WNOHANG) = 0 <0.000027>
13455 09:18:41.616120 sigreturn( <unfinished ...>
13455 09:18:41.616155 <... sigreturn resumed> ) = 1 <0.000029>
13455 09:18:41.616186 accept(3,  <unfinished ...>
13455 09:18:41.616244 <... accept resumed> {sa_family=AF_INET, sin_port=htons(59903), sin_addr=inet_addr("10.146.201.55")}, [16]) = 8 <0.000051>
...
13455 09:18:42.236844 accept(3,  <unfinished ...>
13455 09:18:42.236892 <... accept resumed> {sa_family=AF_INET, sin_port=htons(59273), sin_addr=inet_addr("10.146.201.54")}, [16]) = 8 <0.000036>
What could cause this? The interfaces are:

Code:
# ifconfig -a
bond0     Link encap:Ethernet  Hardware Adresse 40:F2:E9:21:FB:6A  
          inet Adresse:10.146.200.41  Bcast:10.146.200.255  Maske:255.255.255.0
          UP BROADCAST RUNNING MASTER MULTICAST  MTU:1500  Metric:1
          RX packets:12802814 errors:0 dropped:2230 overruns:0 frame:0
          TX packets:24974438 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 Sendewarteschlangenlänge:0 
          RX bytes:1444539093 (1377.6 Mb)  TX bytes:28234489868 (26926.5 Mb)

bond0:L00 Link encap:Ethernet  Hardware Adresse 40:F2:E9:21:FB:6A  
          inet Adresse:10.146.200.40  Bcast:10.146.200.255  Maske:255.255.255.0
          UP BROADCAST RUNNING MASTER MULTICAST  MTU:1500  Metric:1

eth0      Link encap:Ethernet  Hardware Adresse 40:F2:E9:21:FB:6A  
          UP BROADCAST RUNNING SLAVE MULTICAST  MTU:1500  Metric:1
          RX packets:67641 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 Sendewarteschlangenlänge:1000 
          RX bytes:4436676 (4.2 Mb)  TX bytes:0 (0.0 b)
          Speicher:c5a60000-c5a80000 

eth1      Link encap:Ethernet  Hardware Adresse 40:F2:E9:21:FB:6A  
          UP BROADCAST RUNNING SLAVE MULTICAST  MTU:1500  Metric:1
          RX packets:12735173 errors:0 dropped:0 overruns:0 frame:0
          TX packets:24974438 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 Sendewarteschlangenlänge:1000 
          RX bytes:1440102417 (1373.3 Mb)  TX bytes:28234489868 (26926.5 Mb)
          Speicher:c5a40000-c5a60000
Thanks in advance

Matthias