BKG caster does not actively close server connections

[mark@…]

When connecting to BKG casters running 2.0.36, we do not see the server actively closing server connections. Here's a sample tcpdump trace from connecting to the IGS BKG caster:

13:51:41.158599 IP 192.168.1.117.61977 > products.igs-ip.net.rtcm-sc104: Flags [S], seq 3861919486, win 65535, options [mss 1460,nop,wscale 6,nop,nop,TS val 1045387109 ecr 0,sackOK,eol], length 0
13:51:41.357932 IP products.igs-ip.net.rtcm-sc104 > 192.168.1.117.61977: Flags [S.], seq 3009305226, ack 3861919487, win 28960, options [mss 1460,sackOK,TS val 264597231 ecr 1045387109,nop,wscale 7], length 0
13:51:41.358055 IP 192.168.1.117.61977 > products.igs-ip.net.rtcm-sc104: Flags [.], ack 1, win 2058, options [nop,nop,TS val 1045387308 ecr 264597231], length 0
13:51:41.358228 IP 192.168.1.117.61977 > products.igs-ip.net.rtcm-sc104: Flags [P.], seq 1:180, ack 1, win 2058, options [nop,nop,TS val 1045387308 ecr 264597231], length 179
13:51:41.732500 IP products.igs-ip.net.rtcm-sc104 > 192.168.1.117.61977: Flags [.], ack 180, win 235, options [nop,nop,TS val 264597284 ecr 1045387308], length 0
13:51:41.732514 IP products.igs-ip.net.rtcm-sc104 > 192.168.1.117.61977: Flags [P.], seq 1:250, ack 180, win 235, options [nop,nop,TS val 264597284 ecr 1045387308], length 249
13:51:41.732629 IP 192.168.1.117.61977 > products.igs-ip.net.rtcm-sc104: Flags [.], ack 250, win 2054, options [nop,nop,TS val 1045387682 ecr 264597284], length 0
13:51:45.421472 IP products.igs-ip.net.rtcm-sc104 > 192.168.1.117.61977: Flags [P.], seq 250:254, ack 180, win 235, options [nop,nop,TS val 264598246 ecr 1045387682], length 4
13:51:45.421553 IP 192.168.1.117.61977 > products.igs-ip.net.rtcm-sc104: Flags [.], ack 254, win 2054, options [nop,nop,TS val 1045391359 ecr 264598246], length 0
13:51:45.431640 IP products.igs-ip.net.rtcm-sc104 > 192.168.1.117.61977: Flags [.], seq 254:1702, ack 180, win 235, options [nop,nop,TS val 264598247 ecr 1045387682], length 1448
13:51:45.436397 IP products.igs-ip.net.rtcm-sc104 > 192.168.1.117.61977: Flags [.], seq 1702:3150, ack 180, win 235, options [nop,nop,TS val 264598249 ecr 1045387682], length 1448
13:51:45.436451 IP 192.168.1.117.61977 > products.igs-ip.net.rtcm-sc104: Flags [.], ack 3150, win 2025, options [nop,nop,TS val 1045391373 ecr 264598247], length 0
13:51:45.436853 IP products.igs-ip.net.rtcm-sc104 > 192.168.1.117.61977: Flags [.], seq 3150:4598, ack 180, win 235, options [nop,nop,TS val 264598250 ecr 1045387682], length 1448
13:51:45.436894 IP 192.168.1.117.61977 > products.igs-ip.net.rtcm-sc104: Flags [.], ack 4598, win 2048, options [nop,nop,TS val 1045391373 ecr 264598250], length 0
13:51:45.447153 IP products.igs-ip.net.rtcm-sc104 > 192.168.1.117.61977: Flags [.], seq 4598:6046, ack 180, win 235, options [nop,nop,TS val 264598252 ecr 1045387682], length 1448
13:51:45.457043 IP products.igs-ip.net.rtcm-sc104 > 192.168.1.117.61977: Flags [.], seq 6046:7494, ack 180, win 235, options [nop,nop,TS val 264598254 ecr 1045387682], length 1448
13:51:45.457183 IP 192.168.1.117.61977 > products.igs-ip.net.rtcm-sc104: Flags [.], ack 7494, win 2025, options [nop,nop,TS val 1045391392 ecr 264598252], length 0
13:51:45.461294 IP products.igs-ip.net.rtcm-sc104 > 192.168.1.117.61977: Flags [P.], seq 7494:8942, ack 180, win 235, options [nop,nop,TS val 264598255 ecr 1045387682], length 1448
13:51:45.461373 IP 192.168.1.117.61977 > products.igs-ip.net.rtcm-sc104: Flags [.], ack 8942, win 2025, options [nop,nop,TS val 1045391396 ecr 264598255], length 0
13:51:45.636832 IP products.igs-ip.net.rtcm-sc104 > 192.168.1.117.61977: Flags [P.], seq 8942:8987, ack 180, win 235, options [nop,nop,TS val 264598300 ecr 1045391359], length 45
13:51:45.636954 IP 192.168.1.117.61977 > products.igs-ip.net.rtcm-sc104: Flags [.], ack 8987, win 2047, options [nop,nop,TS val 1045391571 ecr 264598300], length 0
13:51:46.160271 IP 192.168.1.117.61977 > products.igs-ip.net.rtcm-sc104: Flags [F.], seq 180, ack 8987, win 2048, options [nop,nop,TS val 1045392094 ecr 264598300], length 0
13:51:46.544689 IP products.igs-ip.net.rtcm-sc104 > 192.168.1.117.61977: Flags [.], ack 181, win 235, options [nop,nop,TS val 264598493 ecr 1045392094], length 0
13:51:50.261404 IP products.igs-ip.net.rtcm-sc104 > 192.168.1.117.61977: Flags [P.], seq 8987:8991, ack 181, win 235, options [nop,nop,TS val 264599456 ecr 1045392094], length 4
13:51:50.261473 IP 192.168.1.117.61977 > products.igs-ip.net.rtcm-sc104: Flags [R], seq 3861919667, win 0, length 0
13:51:50.271394 IP products.igs-ip.net.rtcm-sc104 > 192.168.1.117.61977: Flags [.], seq 8991:10439, ack 181, win 235, options [nop,nop,TS val 264599457 ecr 1045392094], length 1448
13:51:50.271500 IP 192.168.1.117.61977 > products.igs-ip.net.rtcm-sc104: Flags [R], seq 3861919667, win 0, length 0
13:51:50.271560 IP products.igs-ip.net.rtcm-sc104 > 192.168.1.117.61977: Flags [.], seq 10439:11887, ack 181, win 235, options [nop,nop,TS val 264599459 ecr 1045392094], length 1448
13:51:50.271588 IP 192.168.1.117.61977 > products.igs-ip.net.rtcm-sc104: Flags [R], seq 3861919667, win 0, length 0
13:51:50.276586 IP products.igs-ip.net.rtcm-sc104 > 192.168.1.117.61977: Flags [.], seq 11887:13335, ack 181, win 235, options [nop,nop,TS val 264599460 ecr 1045392094], length 1448
13:51:50.276641 IP 192.168.1.117.61977 > products.igs-ip.net.rtcm-sc104: Flags [R], seq 3861919667, win 0, length 0
13:51:50.286193 IP products.igs-ip.net.rtcm-sc104 > 192.168.1.117.61977: Flags [.], seq 13335:14783, ack 181, win 235, options [nop,nop,TS val 264599461 ecr 1045392094], length 1448
13:51:50.286231 IP 192.168.1.117.61977 > products.igs-ip.net.rtcm-sc104: Flags [R], seq 3861919667, win 0, length 0
13:51:50.291241 IP products.igs-ip.net.rtcm-sc104 > 192.168.1.117.61977: Flags [.], seq 14783:16231, ack 181, win 235, options [nop,nop,TS val 264599463 ecr 1045392094], length 1448
13:51:50.291271 IP 192.168.1.117.61977 > products.igs-ip.net.rtcm-sc104: Flags [R], seq 3861919667, win 0, length 0
13:51:50.291639 IP products.igs-ip.net.rtcm-sc104 > 192.168.1.117.61977: Flags [P.], seq 16231:17679, ack 181, win 235, options [nop,nop,TS val 264599464 ecr 1045392094], length 1448
13:51:50.291660 IP 192.168.1.117.61977 > products.igs-ip.net.rtcm-sc104: Flags [R], seq 3861919667, win 0, length 0

From the above, we can see our client sending a FIN on seq 180. The server acknowledges seq 181, but does not send a FIN. The server continues to send data, which the client repeatedly replies with RST.

We see similar behavior from other public BKG casters and from our locally running professional BKG caster.

[stoecker]

Can you make this reproducible? Make short example client showing that behaviour? Does it still happen with recent version?

If that would be a generic problem then BKG casters would overflow soon, as they have a lot of requests in a short time.