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ipv6 sit: work around bogus gcc-8 -Wrestrict warning 

gcc-8 has a new warning that detects overlapping input and output arguments
in memcpy(). It triggers for sit_init_net() calling ipip6_tunnel_clone_6rd(),
which is actually correct:

net/ipv6/sit.c: In function 'sit_init_net':
net/ipv6/sit.c:192:3: error: 'memcpy' source argument is the same as destination [-Werror=restrict]

The problem here is that the logic detecting the memcpy() arguments finds them
to be the same, but the conditional that tests for the input and output of
ipip6_tunnel_clone_6rd() to be identical is not a compile-time constant.

We know that netdev_priv(t->dev) is the same as t for a tunnel device,
and comparing "dev" directly here lets the compiler figure out as well
that 'dev == sitn->fb_tunnel_dev' when called from sit_init_net(), so
it no longer warns.

This code is old, so Cc stable to make sure that we don't get the warning
for older kernels built with new gcc.

Cc: Martin Sebor <msebor@gmail.com>
Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83456
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Arnd Bergmann 2018-02-22 16:55:34 +01:00 committed by David S. Miller
parent 4e14bf4236
commit ca79bec237
1 changed files with 1 additions and 1 deletions
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2
net/ipv6/sit.c
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@ -182,7 +182,7 @@ static void ipip6_tunnel_clone_6rd(struct net_device *dev, struct sit_net *sitn)
#ifdef CONFIG_IPV6_SIT_6RD #ifdef CONFIG_IPV6_SIT_6RD
struct ip_tunnel *t = netdev_priv(dev); struct ip_tunnel *t = netdev_priv(dev);
if (t->dev == sitn->fb_tunnel_dev) { if (dev == sitn->fb_tunnel_dev) {
ipv6_addr_set(&t->ip6rd.prefix, htonl(0x20020000), 0, 0, 0); ipv6_addr_set(&t->ip6rd.prefix, htonl(0x20020000), 0, 0, 0);
t->ip6rd.relay_prefix = 0; t->ip6rd.relay_prefix = 0;
t->ip6rd.prefixlen = 16; t->ip6rd.prefixlen = 16;