Could you send or post the binary .cap file (pcap format) for the packet trace? It is a little hard to read hex. Strictly speaking, it is possible to send an acknowledgement for a FIN because the FIN advances the TCP sequence number. Also if you get a chance, take a look at the TCP state transition diagram in RFC 793, Figure 6 to see whether your handshake matches one of the acceptable teardown flows. Thanks, Dave -----Original Message----- From: linux-net-owner@vger.kernel.org [mailto:linux-net-owner@vger.kernel.org] On Behalf Of Xia Wei-Zhong-W20079 Sent: Monday, September 01, 2003 2:11 AM To: linux-net@vger.kernel.org Subject: extra ack at the end of TCP three-way handshake Hi, there When I were testing my email application, I got below packet sequence. I found there is an extra ack at the end of TCP three-way handshake. Can Linux TCP/IP stack handle this? Also can anyone figure out why server sent this extra ack? Send IP packet through gprsv0 at 125095: 45 00 00 3C 6E 0F 40 00 40 06 DE D6 0A 10 F8 77 E..<n.@.@......w CA 68 20 E6 04 03 00 19 2A 0B 86 A8 00 00 00 00 .h .....*....... A0 02 16 D0 A5 E8 00 00 02 04 05 B4 04 02 08 0A ................ 00 01 E8 A7 00 00 00 00 01 03 03 00 ............ Recv IP packet through gprsv0 at 125165: 45 00 00 28 6E 0F 40 00 35 06 E9 EA CA 68 20 E6 E..(n.@.5....h . 0A 10 F8 77 00 19 04 03 31 C9 C0 50 2A 0B 86 A9 ...w....1..P*... 50 12 00 00 1B 12 00 00 P....... Send IP packet through gprsv0 at 125167: 45 00 00 28 6E 10 40 00 40 06 DE E9 0A 10 F8 77 E..(n.@.@......w CA 68 20 E6 04 03 00 19 2A 0B 86 A9 31 C9 C0 51 .h .....*...1..Q 50 10 16 D0 04 43 00 00 P....C.. Recv IP packet through gprsv0 at 125245: 45 00 00 28 7B B6 00 00 36 06 1B 44 CA 68 20 E6 E..({...6..D.h . 0A 10 F8 77 00 19 04 03 31 C9 C0 51 2A 0B 86 A9 ...w....1..Q*... 50 10 20 00 FB 12 00 00 P. ..... - : send the line "unsubscribe linux-net" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html - : send the line "unsubscribe linux-net" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
