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SubjectRe: [PATCH] ipv4: kernel panic when only one unsecured port available
On Mon, 15 Oct 2007 13:06:14 -0700 (PDT)
David Miller <> wrote:

> From: Andrew Morton <>
> Date: Mon, 15 Oct 2007 12:49:19 -0700
> > This code has recently been reworked, but from my reading, that
> > divide-by-zero can still occur. And given that the numbers in
> > /proc/sys/net/ipv4/ip_local_port_range are inclusive, the arithmetic in
> > inet_csk_get_port() seems to just be wrong?
> >
> > So we have this, against David's current devel tree:
> I'm pretty sure we took care of this, but maybe not :-)


OK, in ipv4_local_port_range() we have

if (range[1] <= range[0])
ret = -EINVAL;

which will prevent the crashes.

But is it good to disallow high=low? This disallows a port range of one
single port. Unless "high" is exclusive. But
Documentation/filesystems/proc.txt says

: ip_local_port_range
: -------------------
: Range of ports used by TCP and UDP to choose the local port. Contains two
: numbers, the first number is the lowest port, the second number the highest
: local port. Default is 1024-4999. Should be changed to 32768-61000 for
: high-usage systems.

ie: inclusive.

Documentation/networking/ip-sysctl.txt says

: ip_local_port_range - 2 INTEGERS
: Defines the local port range that is used by TCP and UDP to
: choose the local port. The first number is the first, the
: second the last local port number. Default value depends on
: amount of memory available on the system:
: > 128Mb 32768-61000
: < 128Mb 1024-4999 or even less.
: This number defines number of active connections, which this
: system can issue simultaneously to systems not supporting
: TCP extensions (timestamps). With tcp_tw_recycle enabled
: (i.e. by default) range 1024-4999 is enough to issue up to
: 2000 connections per second to systems supporting timestamps.

also inclusive.

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