Date: Fri, 8 Oct 2004 23:51:17 +0300 From: Giorgos Keramidas <keramida@freebsd.org> To: Gleb Smirnoff <glebius@freebsd.org> Cc: freebsd-net@freebsd.org Subject: Re: Calling m_pullup in ether_input Message-ID: <20041008205117.GA7818@gothmog.gr> In-Reply-To: <20041008203434.GA2770@cell.sick.ru> References: <20041008151515.GA3136@orion.daedalusnetworks.priv> <20041008203434.GA2770@cell.sick.ru>
next in thread | previous in thread | raw e-mail | index | archive | help
On 2004-10-09 00:34, Gleb Smirnoff <glebius@freebsd.org> wrote: > On Fri, Oct 08, 2004 at 06:15:15PM +0300, Giorgos Keramidas wrote: > G> In ether_input() we unconditionaly discard the mbufs whose m_len is less than > G> ETHER_HDR_LEN. A bit higher M_PKTHDR has been checked but the check made > G> before discarding the frame doesn't pay attention to the m->m_pkthdr.len (the > G> total packet length). > > In my humble opinion, all Ethernet device drivers are intentionally written > in such a way that they always pass an mbuf with contigous Ethernet header > to ether_input(). I know, but thanks for verifying what I had understood so far :-) > Why did you write this patch? Do you really have packet loss? Not really. Just trying to see if there _was_ any packet loss first. After running for several hours, the counters are still zero. I think this means the case of dropped packets would be so rare that there's no real reason to worry too much about lost packets. > G> I am trying to find out how often this happens, by using the attached patch to > G> count the number of small frames received in ether_input() and the number of > G> failed m_pullup() attempts that result from that. > > And what results do you have? I'll keep this change in my workstation for a week or so. No signs of dropped packets yet, though. > G> Does this change seem reasonable as an instrumentation of the particular > G> problem or am I unknowingly breaking something in the way ether_input() is > G> supposed to work? > > AFAIK, this patch does not break anything but just adds more processing. Thanks for the reply. I'm (somewhat slowly) learning more about the way the networking code. A little more processing is a small penalty to pay for trying out things. - Giorgos
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?20041008205117.GA7818>