no ICMP port unreachable for UDP packets

From: clemens (
Date: Tue Jul 24 2001 - 18:14:32 EST

linux 2.4.7 doesn't reply with icmp port unreachable messages to udp packets
to an unbind udp port. strangely the icmp error message is only omitted for
eth0 but not for lo. (i assert it's only been omitted for non local
this behavior has confirmed for 2.4.7-pre8 and 2.4.7-final.

for both udp packets (from lo and from eth0) the icmp_send call in
net/ipv4/udp.c is reached, since UDP_INC_STATS_BH(UdpNoPorts) is called as
you can see from the increasing counter in /proc/net/snmp,
so the reply packet must be drop somewhere in icmp_send.

this bug should be easily reproducable with nmap and tcpdump.

greets, clemens
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to
More majordomo info at
Please read the FAQ at

This archive was generated by hypermail 2b29 : Tue Jul 31 2001 - 21:00:20 EST