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Date: Mon, 04 Jun 2007 12:03:57 +0800 From: Wei Yongjun <yjwei@...fujitsu.com> To: Herbert Xu <herbert@...dor.apana.org.au> CC: netdev@...r.kernel.org Subject: Re: [PATCH] Fix bug of update IPv4 PMTU when received ICMP Fragmentation Needed message > On Mon, Jun 04, 2007 at 08:39:21AM +0800, Wei Yongjun wrote: > >>> Huh? The test new_mtu >= old_mtu should only hold if the sending router >>> is buggy which is what the hack is for. >>> >> Note here old_mtu is not the real old mtu, is the received message's size: >> unsigned short old_mtu = ntohs(iph->tot_len); >> So maybe the patch would like following. >> > > The size of the packet that caused the ICMP is what we want here. That's > why the router must be buggy. > > So I want to know how the route announce a MTU larger then 576, such as 1280? RFC says ICMP error message return as much as we can without exceeding 576 bytes. And ipv4 router alaways return as a packet size 576 because of this. If MTU is greater then 576, HOST will used "mtu = guess_mtu(old_mtu)" to get a MTU. Method of send ICMP Fragmentation Needed message is difference from receive, how can this resolve? Change the method of send ICMP Fragmentation Needed message? I do not think so, the only think we can do is to change the method of receive ICMP message. Do you agree this? -- A new email address of FJWAN is launched from Apr.1 2007. The updated address is: yjwei@...fujitsu.com -------------------------------------------------- Wei Yongjun Development Dept.I Nanjing Fujitsu Nanda Software Tech. Co., Ltd.(FNST) 8/F., Civil Defense Building, No.189 Guangzhou Road, Nanjing, 210029, China TEL: +86+25-86630523-858 COINS: 79955-858 FAX: +86+25-83317685 MAIL: yjwei@...fujitsu.com -------------------------------------------------- - 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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