NETWORK: udp_port_rover reluctant to rove (unlike tcp_port_rover)

From: John Dahlstrom
Date: Sat Jan 15 2005 - 21:39:02 EST


Regarding udp_port_rover (of linux/net/ipv4/udp.c):

In Linux 2.4 or 2.6, I noticed that selected local port numbers for UDP
resist roaming, unlike TCP ports numbers (tcp_port_rover) that appear
to steadily increase irrespective of concurrent local port usage.

What is the advantage of this lack of parallel behavior? (Other than
exacerbating broken behavior of certain firewalls that insist on fixed
UDP source port blocking?)

Aesthetically peculiar it seems, that the kernel reins in port roving
for the connectionless protocol unless a UDP stampede unleashes itself,
while allowing the TCP ports to range free across the local ports
regardless.

Kind regards,

- John

--
http://jodarom.sdf1.org/
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