Date: Fri, 07 Oct 2011 13:02:09 -0400 From: Mike Tancsa <mike@sentex.net> 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: <4E8F3091.6040106@sentex.net> In-Reply-To: <CAFMmRNy%2BFhfhkhHzGibvdesqBW-jVXr87=NGBhSbJXKK7FDpbA@mail.gmail.com> References: <CAFMmRNy%2BFhfhkhHzGibvdesqBW-jVXr87=NGBhSbJXKK7FDpbA@mail.gmail.com>
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On 10/7/2011 11:54 AM, 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). Not sure, but would this not be a "good thing" in some cases ? Having ping behave in this manner would help you discover such PMTU issues no ? ---Mike -- ------------------- Mike Tancsa, tel +1 519 651 3400 Sentex Communications, mike@sentex.net Providing Internet services since 1994 www.sentex.net Cambridge, Ontario Canada http://www.tancsa.com/
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