neigh_params_release() usage in net/ipv6/addrconf.c

Chase Douglas
2009-05-15T16:33:41Z

I'm debugging an issue I'm seeing when I use vlan with IPv6 support.
After bringing up the device, I'm unable to bring it down and
unregister it. I put some debug statements around dev_hold() and
dev_put() to see what was going on:

dev_hold() called on lo.2, new refcnt: 1 (net/core/dev.c:4162)
dev_hold() called on lo.2, new refcnt: 2 (net/core/neighbour.c:1357)
dev_hold() called on lo.2, new refcnt: 3 (net/ipv4/devinet.c:178)
dev_hold() called on lo.2, new refcnt: 4 (net/core/neighbour.c:1357)
dev_hold() called on lo.2, new refcnt: 5 (net/8021q/vlan.c:266)
dev_hold() called on lo.2, new refcnt: 6 (net/core/link_watch.c:219)
dev_put() called on lo.2, new refcnt: 5 (net/core/link_watch.c:191)
dev_hold() called on lo.2, new refcnt: 6 (net/core/dev.c:684)
dev_put() called on lo.2, new refcnt: 5 (net/ipv4/fib_semantics.c:149)
dev_hold() called on lo.2, new refcnt: 6 (net/core/dev.c:684)
dev_hold() called on lo.2, new refcnt: 7 (net/ipv4/fib_frontend.c:173)
dev_put() called on lo.2, new refcnt: 6 (net/ipv4/route.c:2453)
dev_put() called on lo.2, new refcnt: 5 (net/ipv4/fib_semantics.c:149)
dev_put() called on lo.2, new refcnt: 4 (net/core/neighbour.c:1393)
dev_put() called on lo.2, new refcnt: 3 (net/ipv4/devinet.c:151)
dev_put() called on lo.2, new refcnt: 2 (net/core/dev.c:4010)
dev_put() called on lo.2, new refcnt: 1 (net/8021q/vlan.c:182)
unregister_netdevice: waiting for lo.2 to become free. Usage count = 2

The fourth dev_hold() is in neigh_parms_alloc(), called by
ipv6_add_dev(). The only place I see neigh_parms_release() called in
addrconf.c is if ipv6_add_dev() fails later on, or when taking the
device down in addrconf_ifdown(). Unfortunately, when I bring the vlan
dev down I never see addrconf_ifdown() called with the how parameter
set to 1, which is the only instance where neigh_parms_release() would
be called.

Why is neigh_parms_release() called in addrconf_ifdown() instead of
in6_dev_finish_destroy(), which looks to me to be the complement of
ipv6_add_dev()? If neigh_parms_release() really should be called in
addrconf_ifdown(), does anyone know why it's not being called properly
in this instance?

PS: I am running my tests using a slightly modified SLES 11 kernel. I
haven't been able to find anything in the git trees that would
indicate to me that the problem has been fixed upstream.