Message ID | 4EDF1481.1080106@cn.fujitsu.com |
---|---|
State | Accepted, archived |
Delegated to: | David Miller |
Headers | show |
From: Li Wei <lw@cn.fujitsu.com> Date: Wed, 07 Dec 2011 15:23:45 +0800 > There is no obvious reason to add a default multicast route for loopback > devices, otherwise there would be a route entry whose dst.error set to > -ENETUNREACH that would blocking all multicast packets. > > Signed-off-by: Li Wei <lw@cn.fujitsu.com> I still do not understand the purpose of this change, what problems does the current behavior cause? And can you be sure that by making this change, you are not breaking something, somewhere, that depends upon the current behavior? -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
David Miller wrote: > From: Li Wei <lw@cn.fujitsu.com> > Date: Wed, 07 Dec 2011 15:23:45 +0800 > >> There is no obvious reason to add a default multicast route for loopback >> devices, otherwise there would be a route entry whose dst.error set to >> -ENETUNREACH that would blocking all multicast packets. >> >> Signed-off-by: Li Wei <lw@cn.fujitsu.com> > > I still do not understand the purpose of this change, what problems > does the current behavior cause? Hi, David, thank you for your comment. The problem is that the resulting routing table depends on the sequence of interface's initialization and in some situation, that would block all muticast packets. Suppose there are two interfaces on my computer (lo and eth0), if we initailize 'lo' before 'eth0', the resuting routing table(for multicast) would be # ip -6 route show | grep ff00:: unreachable ff00::/8 dev lo metric 256 error -101 ff00::/8 dev eth0 metric 256 When sending multicasting packets, routing subsystem will return the first route entry which with a error set to -101(ENETUNREACH). I know the kernel will set the default ipv6 address for 'lo' when it is up and won't set the default multicast route for it, but there is no reason to stop 'init' program from setting address for 'lo', and that is exactly what systemd did. I am sure there is something wrong with kernel or systemd, currently I preferred kernel caused this problem. > > And can you be sure that by making this change, you are not breaking > something, somewhere, that depends upon the current behavior? > > I can't see there is any reason to set a default multicast route for loopback device *automatically*. Thanks, Wei -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
From: Li Wei <lw@cn.fujitsu.com> Date: Thu, 08 Dec 2011 08:58:21 +0800 > The problem is that the resulting routing table depends on the sequence > of interface's initialization and in some situation, that would block all > muticast packets. Suppose there are two interfaces on my computer > (lo and eth0), if we initailize 'lo' before 'eth0', the resuting routing > table(for multicast) would be > > # ip -6 route show | grep ff00:: > unreachable ff00::/8 dev lo metric 256 error -101 > ff00::/8 dev eth0 metric 256 > > When sending multicasting packets, routing subsystem will return the first > route entry which with a error set to -101(ENETUNREACH). > > I know the kernel will set the default ipv6 address for 'lo' when it is up > and won't set the default multicast route for it, but there is no reason to > stop 'init' program from setting address for 'lo', and that is exactly what > systemd did. Ok, I added this more detailed explanation to the commit message and applied your patch. Probably it is a good idea to explain things completely, with all details and examples, in the commit message from the beginning :-) -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
> From: Li Wei <lw@cn.fujitsu.com> > Date: Thu, 08 Dec 2011 08:58:21 +0800 > >> The problem is that the resulting routing table depends on the sequence >> of interface's initialization and in some situation, that would block all >> muticast packets. Suppose there are two interfaces on my computer >> (lo and eth0), if we initailize 'lo' before 'eth0', the resuting routing >> table(for multicast) would be >> >> # ip -6 route show | grep ff00:: >> unreachable ff00::/8 dev lo metric 256 error -101 >> ff00::/8 dev eth0 metric 256 >> >> When sending multicasting packets, routing subsystem will return the first >> route entry which with a error set to -101(ENETUNREACH). >> >> I know the kernel will set the default ipv6 address for 'lo' when it is up >> and won't set the default multicast route for it, but there is no reason to >> stop 'init' program from setting address for 'lo', and that is exactly what >> systemd did. > > Ok, I added this more detailed explanation to the commit message and > applied your patch. > > Probably it is a good idea to explain things completely, with all details > and examples, in the commit message from the beginning :-) > > Thanks David, remember your advice :) -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c index cf88df8..36806de 100644 --- a/net/ipv6/addrconf.c +++ b/net/ipv6/addrconf.c @@ -1805,7 +1805,8 @@ static struct inet6_dev *addrconf_add_dev(struct net_device *dev) return ERR_PTR(-EACCES); /* Add default multicast route */ - addrconf_add_mroute(dev); + if (!(dev->flags & IFF_LOOPBACK)) + addrconf_add_mroute(dev); /* Add link local route */ addrconf_add_lroute(dev);
There is no obvious reason to add a default multicast route for loopback devices, otherwise there would be a route entry whose dst.error set to -ENETUNREACH that would blocking all multicast packets. Signed-off-by: Li Wei <lw@cn.fujitsu.com> --- net/ipv6/addrconf.c | 3 ++- 1 files changed, 2 insertions(+), 1 deletions(-)