David Miller wrote:
From: Ben Greear <[EMAIL PROTECTED]>
Date: Tue, 04 Sep 2007 15:45:14 -0700
According to the comment in the net/core/sock.c code (in 2.6.20), I should be
able to pass a zero
optlen to the setsockopt method for SO_BINDTODEVICE:
...
However, earlier in that method it returns -EINVAL if optlen is < sizeof(int).
The man page has comments similar to that in the code above.
Also, even when I get the un-bind call working with code similar to:
int z = 0;
setsockopt(s, SOL_SOCKET, SO_BINDTODEVICE, &z, sizeof(z));
The app I'm working on (Xorp) does not appear to work. Perhaps because
the kernel does not clean up the cached route when you un-bind
as it does in the (re)bind logic?
/* Remove any cached route for this socket. */
sk_dst_reset(sk);
Ok, the patch below is how I'm dealing with this.
Let me know if things work better now, and also I would appreciate
it if you could contact the man page maintainers to remove the
optlen==0 language.
Thanks.
From 136f55cf4ad0a3b0185bfc97c68f9e4d74ddcfe7 Mon Sep 17 00:00:00 2001
From: David S. Miller <[EMAIL PROTECTED]>
Date: Fri, 14 Sep 2007 13:10:17 -0700
Subject: [PATCH] [NET]: Fix two issues wrt. SO_BINDTODEVICE.
1) Comments suggest that setting optlen to zero will unbind
the socket from whatever device it might be attached to. This
hasn't been the case since at least 2.2.x because the first thing
this function does is return -EINVAL if 'optlen' is less than
sizeof(int).
Furthermore, there are not "optlen == 0" tests in the
SO_BINDTODEVICE code either.
This also means we can toss the "!valbool" code block because if
that is true we'll also see the first byte of the passed in name
buffer as '\0' and this will also unbind the socket.
From user-space, does this imply that the 'empty string' we use to
unbind must be at least 4 bytes long, but with the first byte /0?
If so, I think it might be confusing for the comments to say use ""
to unbind, since that would not be a long enough chunk of memory.
Maybe something like "Use a character array of at least 4 bytes in
length with the first byte set to '/0'."
This brings up another issue as well: What if the device name is "tr1",
to bind to it we'd have to pass in "tr1/0" and optlen of 4. Not that this
is difficult to do, but it does seem like a weird thing to have to do.
Thanks,
Ben
--
Ben Greear <[EMAIL PROTECTED]>
Candela Technologies Inc http://www.candelatech.com
-
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to [EMAIL PROTECTED]
More majordomo info at http://vger.kernel.org/majordomo-info.html
