Date: Thu, 26 Mar 2015 11:29:30 -0400 From: Karim Fodil-Lemelin <fodillemlinkarim@gmail.com> To: freebsd-net@freebsd.org Subject: Re: Another fragment question / patch Message-ID: <551425DA.3000205@gmail.com> In-Reply-To: <551017D1.60008@gmail.com> References: <550C3A62.3080403@gmail.com> <550C5F6C.3080302@selasky.org> <550C7D0C.3090603@gmail.com> <550D3675.5030900@selasky.org> <551017D1.60008@gmail.com>
next in thread | previous in thread | raw e-mail | index | archive | help
FYI: I've created a bug report for this. Thanks. On 2015-03-23 9:40 AM, Karim Fodil-Lemelin wrote: > On 2015-03-21 5:14 AM, Hans Petter Selasky wrote: >> On 03/20/15 21:03, Karim Fodil-Lemelin wrote: >>> On 2015-03-20 1:57 PM, Hans Petter Selasky wrote: >>>> On 03/20/15 16:18, Karim Fodil-Lemelin wrote: >>>>> Hi, >>>>> >>>>> While reading through a previous comment on this list about fragments >>>>> I've noticed that mbuf tags aren't being copied from the leading >>>>> fragment (header) to the subsequent fragment packets. In other words, >>>>> one would expect that all fragments of a packet are carrying the same >>>>> tags that were set on the original packet. I have built a simple test >>>>> were I use ipfw with ALTQ and sent large packet (bigger then MTU) off >>>>> that BSD machine. I have observed that the leading fragment (m0) >>>>> packet >>>>> is going through the right class although the next fragments are >>>>> hitting >>>>> the default class for unclassified packets. >>>>> >>>>> Here is a patch that makes things works as expected (all fragments >>>>> carry >>>>> the ALTQ tag): >>>>> >>>>> diff --git a/freebsd/sys/netinet/ip_output.c >>>>> b/freebsd/sys/netinet/ip_output.c >>>>> index d650949..7d8f041 100644 >>>>> --- a/freebsd/sys/netinet/ip_output.c >>>>> +++ b/freebsd/sys/netinet/ip_output.c >>>>> @@ -1184,7 +1184,10 @@ smart_frag_failure: >>>>> ipstat.ips_odropped++; >>>>> goto done; >>>>> } >>>>> - m->m_flags |= (m0->m_flags & M_MCAST) | M_FRAG; >>>>> + >>>>> + m->m_flags |= (m0->m_flags & M_COPYFLAGS) | M_FRAG; >>>>> + m_tag_copy_chain(m, m0, M_NOWAIT); >>>>> + >>>>> /* >>>>> * In the first mbuf, leave room for the link >>>>> header, then >>>>> * copy the original IP header including options. >>>>> The >>>>> payload >>>>> diff --git a/freebsd/sys/sys/mbuf.h b/freebsd/sys/sys/mbuf.h >>>>> index 2efff38..6ad8439 100644 >>>>> --- a/freebsd/sys/sys/mbuf.h >>>>> >>>> >>>> Hi, >>>> >>>> I see your point about copying the tags. I'm not sure however that >>>> M_COPYFLAGS is correct, because it also copies M_RDONLY, which is not >>>> relevant for this case. Can you explain what flags need copying in >>>> addition to M_MCAST ? Maybe we need to define these flags separately. >>>> >>>> Thank you! >>>> >>>> --HPS >>> Hi, >>> >>> Arguably the M_RDONLY is added when m_copy() is called a bit later in >>> that function. m_copym() does a shallow copy (through a call to >>> mb_dupcl) and will set the RDONLY flag when doing so. So the fact it >>> was >>> copied over from M_COPYFLAGS shouldn't be a problem in terms of >>> functionality. A similar logic applies to the M_VLANTAG since it should >>> never be set in ip_output() (severe layer violation). I guess >>> M_COPYFLAGS is kinda safe but not necessarily correct. >>> >>> In terms of appropriate behavior (whats the real purpose of >>> M_COPYFLAGS?) my initial patch is debatable and to answer your question >>> I would consider to copy the remaining flags: >>> >>> M_PKTHDR => already in there through the m_gethdr() call >>> M_BCAST => no need to copy >>> M_MCAST => already in there in ip_fragment() >>> M_PROTOFLAGS >>> M_SKIP_FIREWALL => for layer 2 fire-walling? >>> >>> So something like? >>> >>> - m->m_flags |= (m0->m_flags & M_MCAST); >>> + m->m_flags |= (m0->m_flags & (M_MCAST | M_PROTOFLAGS)); >>> + m_tag_copy_chain(m, m0, M_NOWAIT); >>> >> >> Hi, >> >> Could you have a look at the attached patch, test and give some >> comments? I believe the right thing to do in this case is to use the >> copy packet header function. >> >> --HPS >> > Hi, > > Your patch seems to work as well as mine, albeit completely swinging > the other way now since your copying a lot more from the packet header > with the call to m_dup_pkthdr() (including the M_COPYFLAGS, vlan tags, > etc..). > > I think this is fine, one would expect IP fragments to be somewhat > very close to the original packet. > > Thanks, > > Karim. > _______________________________________________ > freebsd-net@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-net > To unsubscribe, send any mail to "freebsd-net-unsubscribe@freebsd.org"
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?551425DA.3000205>