On Tue, Jul 21, 2015 at 12:14 PM, Martin Blumenstingl
<martin.blumensti...@googlemail.com> wrote:
> 9c70776 added validation for the packet size in packet_snd. This change
> enforced that every packet needs a long enough header and at least one
> byte payload.
>
> However, when trying to establish a PPPoE connection the following message
> is printed every time a PPPoE discovery packet is sent:
> pppd: packet size is too short (24 <= 24)
>
> From what I can see in the PPPoE code the "PADI" discovery packet can
> consist of only a header with no payload (when there is neither a service
> name nor a Host-Uniq configured).
Interesting. 9c7077622dd9 only extended the check from tpacket_snd to
packet_snd to make the two paths equivalent. The existing check had the
ominous statement
/* net device doesn't like empty head */
so allowing a header-only packet while correct in your case may not be
safe in some edge cases (specific device drivers?).
This was also discussed previously
http://www.spinics.net/lists/netdev/msg309677.html
In any case, I don't think that reverting the patch and restoring the old
inconsistent state is a fix.
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