Released gor1.3 forwards the same request twice on Linux

[anatoly71]

Hello, I am using macbook, gor1.3.

I deploy two docker containers (linux) exposing an http endpoint each.
They are started with docker-compose so that they can communicate with each other being on the same docker network.

"mock1" linux container:

• http endpont with port 9003
• gor1.3 started with command ./gor1.3 -verbose 3 -input-raw :9003 -output-http http://mock2:9004

"mock2" linux container:

• http endpont with port 9004

I execute tcpdump on the both containers to see requests.

Scenario:: mac host -> linux mock1 (goreplay) -> linux mock2.
I send a request to linux container mock1 (goreplay here) using mapped port 9093, and I expect the request forwarded to linux container mock2. The actual outcome TWO requests forwarded.

on my workstation I execute
curl -v "http://localhost:9093/some/path" -H "accept: application/json"

mock1
tcpdump records ONE incoming request but goreplay reports TWO incoming requests

bash-4.3#tcpdump -Avvs0 -i eth0 'dst port 9003 and (((ip[2:2] - ((ip[0]&0xf)<<2)) - ((tcp[12]&0xf0)>>2)) != 0)'
tcpdump: listening on eth0, link-type EN10MB (Ethernet), capture size 262144 bytes
11:36:00.901910 IP (tos 0x0, ttl 64, id 61123, offset 0, flags [DF], proto TCP (6), length 156)
172.24.0.1.57306 > 20b83084ad91.9003: Flags [P.], cksum 0x58c2 (incorrect -> 0x4cac), seq 1525591779:1525591883, ack 70000080, win 502, options [nop,nop,TS val 1146716091 ecr 3110618404], length 104
E.....@.@..d..........#+Z....,......X......
DY...hE$GET /some/path HTTP/1.1
Host: localhost:9093
User-Agent: curl/7.64.1
accept: application/json

goreplay reports TWO incoming requests (same meta data in the debug output)

bash-4.3# ./gor1.3 -verbose 3 -input-raw :9003 -output-http http://mock2:9004
[DEBUG][elapsed 91.0109ms]: Intercepting traffic from: :[9003]
2021/08/10 11:35:27 [PPID 42 and PID 122] Version:1.3.0
[DEBUG][elapsed 34.7126803s]: [EMITTER] input: 1 dfda232bac180001042c1dd0 1628595360901910500 0 from: Intercepting traffic from: :[9003]
[DEBUG][elapsed 1.6367ms]: [EMITTER] input: 1 dfda232bac180001042c1dd0 1628595360901910500 0 from: Intercepting traffic from: :[9003]

mock2
TWO requests received

bash-4.3# tcpdump -Avvs0 -i eth0 'dst port 9004 and (((ip[2:2] - ((ip[0]&0xf)<<2)) - ((tcp[12]&0xf0)>>2)) != 0)'
tcpdump: listening on eth0, link-type EN10MB (Ethernet), capture size 262144 bytes
11:36:02.527683 IP (tos 0x0, ttl 64, id 50761, offset 0, flags [DF], proto TCP (6), length 175)
scripts_mock1_1.scripts_default.41406 > b9561d25d337.9004: Flags [P.], cksum 0x58d7 (incorrect -> 0x8750), seq 4181280619:4181280742, ack 3794026077, win 502, options [nop,nop,TS val 724414948 ecr 703821815], length 123
E....I@.@.............#,.9Gk.$>]....X......
+-..).w.GET /ftaas/v1/info HTTP/1.1
Host: mock2:9004
User-Agent: curl/7.64.1
Accept: application/json
Accept-Encoding: gzip

11:36:02.530773 IP (tos 0x0, ttl 64, id 46863, offset 0, flags [DF], proto TCP (6), length 175)
scripts_mock1_1.scripts_default.41408 > b9561d25d337.9004: Flags [P.], cksum 0x58d7 (incorrect -> 0x3dc0), seq 1256581563:1256581686, ack 2418861540, win 502, options [nop,nop,TS val 724414951 ecr 703821815], length 123
E.....@.@.+...........#,J....,......X......
+-..).w.GET /ftaas/v1/info HTTP/1.1
Host: mock2:9004
User-Agent: curl/7.64.1
Accept: application/json
Accept-Encoding: gzip

[buger]

Should be fixed now and released as 1.3.1!

[anatoly71]

I've tested 1.3.1 on Linux and the issue is fixed. Thanks a lot!