Re: [PATCH v5] ipv6: Fix problem with expired dst cache

From: Gao feng <redacted>
Date: Mon, 5 Mar 2012 15:16:02 +0800

If the ipv6 dst cache which copy from the dst generated by ICMPV6 RA packet.
this dst cache will not check expire because it has no RTF_EXPIRES flag.
So this dst cache will always be used until the dst gc run.

Change the struct dst_entry,add a union contains new pointer from and expires.
When rt6_info.rt6i_flags has no RTF_EXPIRES flag,the dst.expires has no use.
we can use this field to point to where the dst cache copy from.
The dst.from is only used in IPV6.

In func rt6_check_expired check if rt6_info.dst.from is expired.

In func ip6_rt_copy only set dst.from when the ort has flag RTF_ADDRCONF
and RTF_DEFAULT.then hold the ort.

In func ip6_dst_destroy release the ort.

Add some functions to operate the RTF_EXPIRES flag and expires(from) together.
and change the code to use these new adding functions.

Signed-off-by: Gao feng <redacted>

I see some unprotected access to dst.expires in the router discovery
code in net/ipv6/ndisc.c, doesn't that need to be updated?

There are probably some more similar cases elsewhere in the ipv6 code
too.