ip6: Drop dead code in ip6_input_hbh()

[markj]

Summary

After commit 069a67374ed9, ip6_input() quickly rejects packets with
plen == 0, before ip6_input_hbh() is called. So, there is no need to
check this condition again in the helper function.

[bms]

This comment was removed by bms.

[zlei]

sys/netinet6/ip6_input.c

434

Shall those stats be moved to ip6_input(), after the checking if (plen == 0) ?

[markj]

sys/netinet6/ip6_input.c

434

ifs6_in_discard is handled already. We should increment ifs6_in_hdrerr too I think.

Is ip6s_badoptions still correct? Probably it should be ip6s_tooshort instead?

[markj]

• increment more counters
• add a branch annotation

[zlei]

Looks good to me.

sys/netinet6/ip6_input.c

434

The ifs6_in_hdrerr was to indicate a packet without JumboPayload option, since

If the payload length field is 0 and the next header field indicates Hop-by-Hop Options header

Since we do not support / check JumboPayload option, then ip6s_tooshort looks reasonable.

CC the original author @bz to see if he has any thoughts about it.