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Date: Mon, 27 Jul 2015 20:06:07 +0000 From: "bugzilla-dae...@bugzilla.kernel.org" <bugzilla-dae...@bugzilla.kernel.org> To: "shemmin...@linux-foundation.org" <shemmin...@linux-foundation.org> Subject: [Bug 102051] New: Unexpected TCP behavior https://bugzilla.kernel.org/show_bug.cgi?id=102051 Bug ID: 102051 Summary: Unexpected TCP behavior Product: Networking Version: 2.5 Kernel Version: 3.19 Hardware: All OS: Linux Tree: Mainline Status: NEW Severity: low Priority: P1 Component: IPV4 Assignee: shemmin...@linux-foundation.org Reporter: vreme...@gmail.com Regression: No While running nmap against localhost I started to see open ports in the dynamic range (>1024). Kind of odd, knowing netstat and ss did not show any listeners on the port. With tcpdump, I confirmed system was returning S/ACK for ports that did not have a listener enabled. The "issue" or feature only occurs if source port matches the destination port. # netstat -nap | grep 5000 # $ nc localhost -p 5000 5000 a a # tcpdump -i lo port 5000 14:28:18.059708 IP 127.0.0.1.5000 > 127.0.0.1.5000: Flags [S], seq 2005295207, win 43690, options [mss 65495,sackOK,TS val 4481790 ecr 0,nop,wscale 7], length 0 14:28:18.059721 IP 127.0.0.1.5000 > 127.0.0.1.5000: Flags [S.], seq 2005295207, ack 2005295208, win 43690, options [mss 65495,sackOK,TS val 4481790 ecr 4481790,nop,wscale 7], length 0 14:28:18.059729 IP 127.0.0.1.5000 > 127.0.0.1.5000: Flags [.], ack 2005295208, win 342, options [nop,nop,TS val 4481790 ecr 4481790], length 0 14:28:19.121392 IP 127.0.0.1.5000 > 127.0.0.1.5000: Flags [P.], seq 2005295208:2005295210, ack 2005295208, win 342, options [nop,nop,TS val 4482056 ecr 4481790], length 2 14:28:19.121407 IP 127.0.0.1.5000 > 127.0.0.1.5000: Flags [.], ack 2005295210, win 342, options [nop,nop,TS val 4482056 ecr 4482056], length 0 # hping3 -S 127.0.0.1 -p 5000 -s 5000 HPING 127.0.0.1 (lo 127.0.0.1): S set, 40 headers + 0 data bytes len=40 ip=127.0.0.1 ttl=64 id=2036 sport=5000 flags=S seq=0 win=512 rtt=3.8 ms << SYN DUP! len=52 ip=127.0.0.1 ttl=64 DF id=670 sport=5000 flags=A seq=0 win=342 rtt=3.8 ms << SYN/ACK len=40 ip=127.0.0.1 ttl=64 DF id=43435 sport=5000 flags=RA seq=1 win=0 rtt=3.7 ms I confirmed it with nmap, nc, and hping3; granted they build on same c libraries, so I am not even sure if this should be filed as a kernel bug (or even a bug); just did not expect to see this behavior // Expected to see a RST instead. -- You are receiving this mail because: You are the assignee for the bug. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
