Date: Thu, 2 Aug 2007 15:15:23 -0700 From: "Jack Vogel" <jfvogel@gmail.com> To: "Andre Oppermann" <andre@freebsd.org>, "freebsd-net@freebsd.org" <freebsd-net@freebsd.org> Subject: Re: Odd driver behavior with IPV6 Message-ID: <2a41acea0708021515v118a6087ge6ddbfe415cb3774@mail.gmail.com> In-Reply-To: <2a41acea0708021444o7edc4ecetb08601fa18ad43ea@mail.gmail.com> References: <2a41acea0708021444o7edc4ecetb08601fa18ad43ea@mail.gmail.com>
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On 8/2/07, Jack Vogel <jfvogel@gmail.com> wrote: > I have some behavior I don't understand, perhaps someone can enlighten me. > > There is a difference in behavior between the em driver and ixgbe, but I can > not figure out what it is, here is the behavior. > > With em driver, you can give the interface an ipv6 address, and set mtu > to 9000, then when you 'route get -inet6 ipv6host' it will show the mtu > to be 9000, this is what you would expect. > > OK, the problem is that with ixgbe, when it is built in OR when it is set > to load immediately on boot it works correctly, BUT, if I just randomly > load the driver after coming up, and then do the above steps, when you > do the route get the MTU shows up only as 1500. This works correctly > for IPv4 which is why this mystifies me, the driver doesnt have any > code for IP versions. > > I hope this explanation is clear. Anyone have a clue? I have some more data, in setup, after the call to ether_ifattach(), the ixgbe driver explicitly does ifp->if_mtu = 9000 to change the default. If I take this out then this all works, but I don't understand why this should be, especially since if the code is static in the kernel it works. Very strange :( Jack PS. BTW, the mxge does this as well, Drew you might want to check if this happens for you.
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