On Tue, 11 Sep 2012, Patrick McHardy wrote:
On Fri, 7 Sep 2012, Fengguang Wu wrote:
Hi Patrick,
FYI, there are new compile warnings show up in
tree: git://gitorious.org/linux-can/linux-can-next master
head: bbe660a7ddf32dfe80753c6722e141bf7e4bf5d8
commit: 4cdd34084d539c758d00c5dc7bf95db2e4f2bc70 [239/293] netfilter:
nf_conntrack_ipv6: improve fragmentation handling
config: avr32-atngw100_defconfig (attached as .config)
All error/warnings:
net/ipv6/netfilter/nf_conntrack_l3proto_ipv6.c: In function
'__ipv6_conntrack_in':
net/ipv6/netfilter/nf_conntrack_l3proto_ipv6.c:231: warning: passing
argument 4 of 'NF_HOOK_THRESH' discards qualifiers from pointer target type
net/ipv6/netfilter/nf_conntrack_l3proto_ipv6.c:231: warning: passing
argument 5 of 'NF_HOOK_THRESH' discards qualifiers from pointer target type
Thanks, I'll look into this.
It seems the cure for this is worse than the problem. The code
currently casts the const struct net_device pointer to non-const
for the NF_HOOK_THRES call. To avoid the cast we'd have to change
all netfilter hooks to take a non-const pointer. The alternative
would be to change the NF_HOOK functions to also take a const struct
net_device pointer, but that would require the same cast to non-const
for nf_queue, which uses dev_hold() and dev_put(), so this would
effectively just move the warning to a different place.
nf_queue is a quite special case, normally netfilter hooks shouln't
be changing anything on the net_device, so I don't want to unconstify
the arguments.
The compiler actually shouldn't warn about this since its an explicit
cast. I know some older versions of gcc did this, but there's no warning
with current versions of gcc and the same casts are already present
in other parts of IPv6 conntrack.
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