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Subject: Socket bound to 0.0.0.0 never receives broadcasts with non-zero IP
 source address
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I noticed that the socket bound to '0.0.0.0' only receives UDP 
broadcasts when they are sent from zero IP: 0.0.0.0->255.255.255.255. 
When the source IP is not zeros, but some valid IP on that network, 
socket never receives such broadcast.

I compared two packets in wireshark as they arrive, and the only 
difference on Ether/IP/UDP level is source IP.

Is there any reason why source IP address would influence the reception 
of the broadcast packets?

I use this python3 program to create bound socket and listen:
#!/usr/bin/env python3.4
import socket
sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM, socket.IPPROTO_UDP)
sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
sock.setsockopt(socket.SOL_SOCKET, socket.SO_BROADCAST, 1)
sock.bind(('0.0.0.0', 67))
print("Waiting for broadcast")
(data, flags, ancillary, addr) = sock.recvmsg(4096, 256)
print("Received broadcast packet")

I use dhclient to send broadcast packets. It sends with src=0.0.0.0 when 
no /var/db/dhclient.leases.* exists, and it always sends with 
src=<previous lease> when the previous lease exists.

10.1 STABLE

Yuri