Date: Mon, 27 Feb 2006 10:50:32 -0800 (PST) From: Doug Ambrisko <ambrisko@ambrisko.com> To: Gleb Smirnoff <glebius@freebsd.org> Cc: Josef Karthauser <joe@tao.org.uk>, net@freebsd.org Subject: Re: Default gateway - wrong interface. ! Message-ID: <200602271850.k1RIoWMg080532@ambrisko.com> In-Reply-To: <20060226102756.GE55275@FreeBSD.org>
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Gleb Smirnoff writes:
| On Sun, Feb 19, 2006 at 03:14:35PM +0000, Josef Karthauser wrote:
| J> I'm guessing that this is a bug (or feature!).
|
| This is not a bug, nor a feature. This is a feature, that hasn't
| been implemented to the end.
|
| Historically, the routes in kernel were static. And they are static
| now. Historically, BSD won't permit you to install same IP addresses,
| or even addresses in the same subnet, on different interfaces. Now,
| FreeBSD permits addresses in the same subnet. But route entries are
| still static, and aren't reconfigring when an interface changes its
| flags.
|
| J> I've got a machine with a wlan interface (iwi0), with an ipv4 network
| J> address and a default gateway. I also have an ethernet card in the same
| J> machine (em0) with the same IP address. The idea is that I can bring
| J> the wireless down, and the wired interface up to get fast transfers when
| J> approriate, and be wireless the rest of the time.
| J>
| J> That works fine, apart from the default gateway:
| J>
| J> # ifconfig iwi0 down
| J> # ifconfig em0 up
| J> # arp -ad
| J> # netstat -rn
| J> Internet:
| J> Destination Gateway Flags Refs Use Netif
| J> Expire
| J> default 87.74.4.33 UGS 0 123 iwi0
| J> 87.74.4.32/27 link#3 UC 0 0 em0
| J> 87.74.4.33 00:90:d0:02:3f:16 UHLW 2 1 em0
| J> 87.74.4.34 00:d0:b7:88:c8:20 UHLW 1 1191414 em0
| J> 127.0.0.1 127.0.0.1 UH 0 2 lo0
| J>
| J> Notice, the local subnet is off the em0, but the default route is still
| J> wired off the iwi0.
| J>
| J> # route delete default
| J> # route add default 87.74.4.33
| J> # netstat -rn
| J> Internet:
| J> Destination Gateway Flags Refs Use Netif
| J> Expire
| J> default 87.74.4.33 UGS 0 123 iwi0
| J> 87.74.4.32/27 link#3 UC 0 0 em0
| J> 87.74.4.33 00:90:d0:02:3f:16 UHLW 2 1 em0
| J> 87.74.4.34 00:d0:b7:88:c8:20 UHLW 1 1191414 em0
| J> 127.0.0.1 127.0.0.1 UH 0 2 lo0
| J>
| J> The default route is _still_ off iwi0; but should be off em0.
| J>
| J> There's obviously something dumb doing on here. Why does the default
| J> route have to be nailed to an interface? It's clear that 87.74.4.33 is
| J> available from em0 as far as the routing table is concerned.
FWIW, we have a patch here for 4.X that deals with this:
Index: sys/net/if.c
===================================================================
RCS file: /usr/local/cvsroot/freebsd/src/sys/net/if.c,v
retrieving revision 1.85.2.25
diff -u -p -r1.85.2.25 if.c
--- sys/net/if.c 28 Nov 2003 15:09:03 -0000 1.85.2.25
+++ sys/net/if.c 14 Oct 2004 03:49:08 -0000
@@ -553,6 +553,7 @@ ifa_ifwithaddr(addr)
#define equal(a1, a2) \
(bcmp((caddr_t)(a1), (caddr_t)(a2), ((struct sockaddr *)(a1))->sa_len) == 0)
TAILQ_FOREACH(ifp, &ifnet, if_link)
+ if (ifp->if_flags & IFF_UP)
TAILQ_FOREACH(ifa, &ifp->if_addrhead, ifa_link) {
if (ifa->ifa_addr->sa_family != addr->sa_family)
continue;
@@ -578,7 +579,7 @@ ifa_ifwithdstaddr(addr)
register struct ifaddr *ifa;
TAILQ_FOREACH(ifp, &ifnet, if_link)
- if (ifp->if_flags & IFF_POINTOPOINT)
+ if (ifp->if_flags & IFF_POINTOPOINT && ifp->if_flags & IFF_UP)
TAILQ_FOREACH(ifa, &ifp->if_addrhead, ifa_link) {
if (ifa->ifa_addr->sa_family != addr->sa_family)
continue;
@@ -617,6 +618,7 @@ ifa_ifwithnet(addr)
* addresses in this address family.
*/
TAILQ_FOREACH(ifp, &ifnet, if_link) {
+ if (ifp->if_flags & IFF_UP)
TAILQ_FOREACH(ifa, &ifp->if_addrhead, ifa_link) {
register char *cp, *cp2, *cp3;
I had to fix a couple of these since we up/down NIC's like you say.
We also have a local patch to make some NIC to just turn off/on the
RX & TX stuff during a down/up so that the NIC doesn't re-initialize.
I'm not sure how well it fits in with -current and that future network
changes. If the network guys would like this added I could do it.
Doug A.
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