UDP/IPv6 handling

[Tom Pusateri]

Lots of embedded devices (like Cisco IP Phones) send TFTP requests with 0 checksums. 

Tom



> On Oct 1, 2014, at 12:58 PM, Michael Tuexen <Michael.Tuexen at lurchi.franken.de> wrote:
> 
> Dear all,
> 
> in udp6_input() we have the following code:
> 
>    if (nxt == IPPROTO_UDP && plen != ulen) {
>        UDPSTAT_INC(udps_badlen);
>        goto badunlocked;
>    } 
>    /*
>     * Checksum extended UDP header and data.
>     */
>    if (uh->uh_sum == 0) {
>        if (ulen > plen || ulen < sizeof(struct udphdr)) {
>            UDPSTAT_INC(udps_nosum);
>            goto badunlocked;
>        }
>    }
> 
> I'm trying to understand the UDP code path...
> 
> 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.
> 
> I think we should check for ulen < sizeof(struct udphdr) in any case.
> 
> Opinions?
> 
> Best regards
> Michael
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