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Subject: Re: UDP/IPv6 handling
From: Michael Tuexen <Michael.Tuexen@lurchi.franken.de>
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Date: Thu, 2 Oct 2014 09:23:05 +0200
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To: Tom Pusateri <pusateri@bangj.com>
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On 02 Oct 2014, at 01:34, Tom Pusateri <pusateri@bangj.com> wrote:

> Lots of embedded devices (like Cisco IP Phones) send TFTP requests =
with 0 checksums.=20
I guess this uses UDP/IPv4, where FreeBSD supports UDP with zero =
checksum.
For UDP/IPv6 this doesn't work. Right after the cited code, the checksum =
is always
checked...

Best regards
Michael
>=20
> Tom
>=20
>=20
>=20
>> On Oct 1, 2014, at 12:58 PM, Michael Tuexen =
<Michael.Tuexen@lurchi.franken.de> wrote:
>>=20
>> Dear all,
>>=20
>> in udp6_input() we have the following code:
>>=20
>>   if (nxt =3D=3D IPPROTO_UDP && plen !=3D ulen) {
>>       UDPSTAT_INC(udps_badlen);
>>       goto badunlocked;
>>   }=20
>>   /*
>>    * Checksum extended UDP header and data.
>>    */
>>   if (uh->uh_sum =3D=3D 0) {
>>       if (ulen > plen || ulen < sizeof(struct udphdr)) {
>>           UDPSTAT_INC(udps_nosum);
>>           goto badunlocked;
>>       }
>>   }
>>=20
>> I'm trying to understand the UDP code path...
>>=20
>> So (ulen > plen) can't be true. I'm wondering why do we only check =
the ulen is not too
>> short only in the case when the UDP checksum is zero. A zero checksum =
should also never happen.
>>=20
>> I think we should check for ulen < sizeof(struct udphdr) in any case.
>>=20
>> Opinions?
>>=20
>> Best regards
>> Michael
>> _______________________________________________
>> 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"
>=20