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Date: Fri, 27 Jun 2014 08:42:05 +0900 From: "jungwon park" <jwpark2@...tecode.co.kr> To: <netdev@...r.kernel.org> Subject: GRO issue with kernel 3.4.94 (icmp fragmentation needed) When using the linux router is turned on GRO, router send the 'fragmentation needed' packets to the sender. and the sender's packets are dropped. The router seems to handle the larger than MTU(1500) with TCP segments by GRO. topology : [Host A] - [Linux Router] - [Host B] kernel : 3.4.94 GRO : on MTU : 1500 tcpdmp : 10:36:36.592752 IP (tos 0x0, ttl 127, id 15685, offset 0, flags [DF], proto TCP (6), length 198) x.x.x.x.49512 > x.x.x.x.445: P 908:1066(158) ack 587 win 254 10:36:36.592911 IP (tos 0x0, ttl 128, id 9712, offset 0, flags [DF], proto TCP (6), length 117) x.x.x.x.445 > x.x.x.x.49512: P 587:664(77) ack 1066 win 252 10:36:36.594552 IP (tos 0x0, ttl 127, id 15686, offset 0, flags [DF], proto TCP (6), length 390) x.x.x.x.49512 > x.x.x.x.445: P 1066:1416(350) ack 664 win 254 10:36:36.596544 IP (tos 0x0, ttl 128, id 9713, offset 0, flags [DF], proto TCP (6), length 2960) x.x.x.x.445 > x.x.x.x.49512: . 664:3584(2920) ack 1416 win 251 10:36:36.596566 IP (tos 0xc0, ttl 64, id 8339, offset 0, flags [none], proto ICMP (1), length 576) x.x.x.x > x.x.x.x: ICMP x.x.x.x unreachable - need to frag (mtu 1500), length 556 IP (tos 0x0, ttl 128, id 9713, offset 0, flags [DF], proto TCP (6), length 2960) x.x.x.x.445 > x.x.x.x.49512: tcp 2940 [bad hdr length 0 - too short, < 20][|icmp] When I turned off GRO, the router operate normally, and there is no problem. and with 3.4.91 kernel, the router has no problem. I doubt 'ipv4: ip_forward: fix inverted local_df test' patch. (http://patchwork.ozlabs.org/patch/345509/) When I revert this patch, the router has no problem. (sorry my poor english.) -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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