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8f34e53b60
Nik reported a bug with pcpu dst cache when nexthop objects are
used illustrated by the following:
$ ip netns add foo
$ ip -netns foo li set lo up
$ ip -netns foo addr add 2001:db8:11::1/128 dev lo
$ ip netns exec foo sysctl net.ipv6.conf.all.forwarding=1
$ ip li add veth1 type veth peer name veth2
$ ip li set veth1 up
$ ip addr add 2001:db8:10::1/64 dev veth1
$ ip li set dev veth2 netns foo
$ ip -netns foo li set veth2 up
$ ip -netns foo addr add 2001:db8:10::2/64 dev veth2
$ ip -6 nexthop add id 100 via 2001:db8:10::2 dev veth1
$ ip -6 route add 2001:db8:11::1/128 nhid 100
Create a pcpu entry on cpu 0:
$ taskset -a -c 0 ip -6 route get 2001:db8:11::1
Re-add the route entry:
$ ip -6 ro del 2001:db8:11::1
$ ip -6 route add 2001:db8:11::1/128 nhid 100
Route get on cpu 0 returns the stale pcpu:
$ taskset -a -c 0 ip -6 route get 2001:db8:11::1
RTNETLINK answers: Network is unreachable
While cpu 1 works:
$ taskset -a -c 1 ip -6 route get 2001:db8:11::1
2001:db8:11::1 from :: via 2001:db8:10::2 dev veth1 src 2001:db8:10::1 metric 1024 pref medium
Conversion of FIB entries to work with external nexthop objects
missed an important difference between IPv4 and IPv6 - how dst
entries are invalidated when the FIB changes. IPv4 has a per-network
namespace generation id (rt_genid) that is bumped on changes to the FIB.
Checking if a dst_entry is still valid means comparing rt_genid in the
rtable to the current value of rt_genid for the namespace.
IPv6 also has a per network namespace counter, fib6_sernum, but the
count is saved per fib6_node. With the per-node counter only dst_entries
based on fib entries under the node are invalidated when changes are
made to the routes - limiting the scope of invalidations. IPv6 uses a
reference in the rt6_info, 'from', to track the corresponding fib entry
used to create the dst_entry. When validating a dst_entry, the 'from'
is used to backtrack to the fib6_node and check the sernum of it to the
cookie passed to the dst_check operation.
With the inline format (nexthop definition inline with the fib6_info),
dst_entries cached in the fib6_nh have a 1:1 correlation between fib
entries, nexthop data and dst_entries. With external nexthops, IPv6
looks more like IPv4 which means multiple fib entries across disparate
fib6_nodes can all reference the same fib6_nh. That means validation
of dst_entries based on external nexthops needs to use the IPv4 format
- the per-network namespace counter.
Add sernum to rt6_info and set it when creating a pcpu dst entry. Update
rt6_get_cookie to return sernum if it is set and update dst_check for
IPv6 to look for sernum set and based the check on it if so. Finally,
rt6_get_pcpu_route needs to validate the cached entry before returning
a pcpu entry (similar to the rt_cache_valid calls in __mkroute_input and
__mkroute_output for IPv4).
This problem only affects routes using the new, external nexthops.
Thanks to the kbuild test robot for catching the IS_ENABLED needed
around rt_genid_ipv6 before I sent this out.
Fixes:
|
||
|---|---|---|
| .. | ||
| 6lowpan | ||
| 9p | ||
| 802 | ||
| 8021q | ||
| appletalk | ||
| atm | ||
| ax25 | ||
| batman-adv | ||
| bluetooth | ||
| bpf | ||
| bpfilter | ||
| bridge | ||
| caif | ||
| can | ||
| ceph | ||
| core | ||
| dcb | ||
| dccp | ||
| decnet | ||
| dns_resolver | ||
| dsa | ||
| ethernet | ||
| ethtool | ||
| hsr | ||
| ieee802154 | ||
| ife | ||
| ipv4 | ||
| ipv6 | ||
| iucv | ||
| kcm | ||
| key | ||
| l2tp | ||
| l3mdev | ||
| lapb | ||
| llc | ||
| mac80211 | ||
| mac802154 | ||
| mpls | ||
| mptcp | ||
| ncsi | ||
| netfilter | ||
| netlabel | ||
| netlink | ||
| netrom | ||
| nfc | ||
| nsh | ||
| openvswitch | ||
| packet | ||
| phonet | ||
| psample | ||
| qrtr | ||
| rds | ||
| rfkill | ||
| rose | ||
| rxrpc | ||
| sched | ||
| sctp | ||
| smc | ||
| strparser | ||
| sunrpc | ||
| switchdev | ||
| tipc | ||
| tls | ||
| unix | ||
| vmw_vsock | ||
| wimax | ||
| wireless | ||
| x25 | ||
| xdp | ||
| xfrm | ||
| compat.c | ||
| Kconfig | ||
| Makefile | ||
| socket.c | ||
| sysctl_net.c | ||