Bug 197511 (bpf) - BPF --> Interactions with Dhclient, Tcpdump, and Network Connections (Ping)
Summary: BPF --> Interactions with Dhclient, Tcpdump, and Network Connections (Ping)
Status: New
Alias: bpf
Product: Base System
Classification: Unclassified
Component: bin (show other bugs)
Version: 10.1-STABLE
Hardware: amd64 Any
: --- Affects Only Me
Assignee: freebsd-net (Nobody)
Depends on:
Reported: 2015-02-10 10:55 UTC by Gary Tivey
Modified: 2020-10-20 17:35 UTC (History)
3 users (show)

See Also:


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Description Gary Tivey 2015-02-10 10:55:52 UTC
Have noticed on a recent install of FreeBSD 10.1 network firewall (pf) ,by accident, that if I enable tcpdump on the external interface, I can easily obtain an IP address via Dhclient on a Comcast cable network. If I close the Tcpdump program, I can no longer ping external ip's such as google dns, or the IPV6 endpoint of a 6-4 tunnel. Once I restart the Tcpdump program, all connectivity is restored. I believe the code in common is the bpf (Berkley Packet Filter). 

Have observed the same behavior using FreeBSD 9.3 on the same hardware.
Seems rather odd that I need to have tcpdump running all the time on this firewall. Condition is persistant through reboots. Devices noted in /dev are bpf, and bpf0. Should there be more bpf devices? I remember a while back the kernel options allowed a number option... is that still the case?
Comment 1 Gary Tivey 2015-02-11 20:31:21 UTC
network interfaces are RealTek , re0 and re1