Date: Sat, 17 Nov 2007 13:08:03 -0800 From: "Kip Macy" <kip.macy@gmail.com> To: "Denis Shaposhnikov" <dsh@vlink.ru> Cc: Mike Silbersack <silby@freebsd.org>, freebsd-current@freebsd.org, Andre Oppermann <andre@freebsd.org> Subject: Re: bizarre em + TSO + MSS issue in RELENG_7 Message-ID: <b1fa29170711171308x62a6371dnbb939748c5c59ae2@mail.gmail.com> In-Reply-To: <20071117213316.499be43b@vlink.ru> References: <20071117003504.R31357@mindcrime.int.bit0.com> <20071117213316.499be43b@vlink.ru>
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On Nov 17, 2007 10:33 AM, Denis Shaposhnikov <dsh@vlink.ru> wrote: > On Sat, 17 Nov 2007 00:42:54 -0500 (EST) > Mike Andrews <mandrews@bit0.com> wrote: > > > Has anyone run into problems with MSS not being respected when using > > TSO, specifically on em cards? > > Yes, I wrote about this problem on the beginning of 2007, see > > http://tinyurl.com/3e5ak5 > if_em.c:3502 /* * Payload size per packet w/o any headers. * Length of all headers up to payload. */ TXD->tcp_seg_setup.fields.mss = htole16(mp->m_pkthdr.tso_segsz); TXD->tcp_seg_setup.fields.hdr_len = hdr_len; Please print out the value of tso_segsz here. It appears to be being set correctly. The only thing I can think of is that t_maxopd is not correct. As tso_segsz is correct here: if (tso) { m->m_pkthdr.csum_flags = CSUM_TSO; m->m_pkthdr.tso_segsz = tp->t_maxopd - optlen; } But maxopd appears to be set correctly in tcp_input: mss = min(mss, offer); /* * maxopd stores the maximum length of data AND options * in a segment; maxseg is the amount of data in a normal * segment. We need to store this value (maxopd) apart * from maxseg, because now every segment carries options * and thus we normally have somewhat less data in segments. */ tp->t_maxopd = mss;
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