kern/50456: alc - packet loose when tcpdump

[freddy.dsx+netbsd%free.fr@localhost]

>Number:         50456
>Category:       kern
>Synopsis:       alc - packet loose when tcpdump
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sat Nov 21 12:15:00 +0000 2015
>Originator:     freddy dissaux
>Release:        NetBSD 7.0
>Organization:
>Environment:
NetBSD n7010.bsdsx.fr 7.0 NetBSD 7.0 (GENERIC) #1: Sat Nov 21 13:36:17 CET 2015  root%n7010.bsdsx.fr@localhost:/usr/src/sys/arch/amd64/compile/GENERIC amd64

>Description:
When tcpdump on alc, some packets are lost:

dsx@n7010>ping 172.16.40.1
PING 172.16.40.1 (172.16.40.1): 56 data bytes
64 bytes from 172.16.40.1: icmp_seq=0 ttl=64 time=0.972398 ms
64 bytes from 172.16.40.1: icmp_seq=1 ttl=64 time=0.921371 ms
# sudo tcpdump -n -i alc0 not port ssh
64 bytes from 172.16.40.1: icmp_seq=8 ttl=64 time=1.025976 ms
64 bytes from 172.16.40.1: icmp_seq=9 ttl=64 time=0.911102 ms
64 bytes from 172.16.40.1: icmp_seq=10 ttl=64 time=0.948231 ms
# ^C tcpdump
64 bytes from 172.16.40.1: icmp_seq=18 ttl=64 time=0.954294 ms
64 bytes from 172.16.40.1: icmp_seq=19 ttl=64 time=0.907106 ms
^C
----172.16.40.1 PING Statistics----
20 packets transmitted, 7 packets received, 65.0% packet loss
round-trip min/avg/max/stddev = 0.907106/0.948640/1.025976/0.041744 ms
>How-To-Repeat:
- configure an alc interface
- ping the gateway
- tcpdump on alc
>Fix:
Patch based on OpenBSD's sys/dev/pci/if_alc.c rev 1.36 follow