Date: Fri, 07 Oct 2011 18:42:34 +0200 From: Andre Oppermann <andre@freebsd.org> To: Ryan Stone <rysto32@gmail.com> Cc: freebsd-net <freebsd-net@freebsd.org> Subject: Re: [PATCH] Don't have ICMP Echo Replies copy fragmentation flags from Echo Request Message-ID: <4E8F2BFA.7020002@freebsd.org> In-Reply-To: <CAFMmRNy%2BFhfhkhHzGibvdesqBW-jVXr87=NGBhSbJXKK7FDpbA@mail.gmail.com> References: <CAFMmRNy%2BFhfhkhHzGibvdesqBW-jVXr87=NGBhSbJXKK7FDpbA@mail.gmail.com>
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On 07.10.2011 17:54, Ryan Stone wrote: > Currently when FreeBSD responds to a ICMP Echo Request, it takes the > original mbuf, rewrites a couple of fields (like the src/dst IP and > the ICMP type), and then sends that mbuf back. As things are > currently implemented, the Don't Fragment bit is kept in the ICMP > replay. This can cause problems for large ICMP Echo Requests if the > MTU on the return route is less than the MTU on the incoming route and > the DF bit is set(Linux's ping command sets it by default). Is it > intended that the DF bit from the Request be copied into the Reply? Yes, this is intended. It allows you to test asymmetric paths. -- Andre
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