net: use struct_group to copy ip/ipv6 header addresses

kernel test robot reported warnings when build bonding module with
make W=1 O=build_dir ARCH=x86_64 SHELL=/bin/bash drivers/net/bonding/:

                 from ../drivers/net/bonding/bond_main.c:35:
In function ‘fortify_memcpy_chk’,
    inlined from ‘iph_to_flow_copy_v4addrs’ at ../include/net/ip.h:566:2,
    inlined from ‘bond_flow_ip’ at ../drivers/net/bonding/bond_main.c:3984:3:
../include/linux/fortify-string.h:413:25: warning: call to ‘__read_overflow2_field’ declared with attribute warning: detected read beyond size of f
ield (2nd parameter); maybe use struct_group()? [-Wattribute-warning]
  413 |                         __read_overflow2_field(q_size_field, size);
      |                         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In function ‘fortify_memcpy_chk’,
    inlined from ‘iph_to_flow_copy_v6addrs’ at ../include/net/ipv6.h:900:2,
    inlined from ‘bond_flow_ip’ at ../drivers/net/bonding/bond_main.c:3994:3:
../include/linux/fortify-string.h:413:25: warning: call to ‘__read_overflow2_field’ declared with attribute warning: detected read beyond size of f
ield (2nd parameter); maybe use struct_group()? [-Wattribute-warning]
  413 |                         __read_overflow2_field(q_size_field, size);
      |                         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

This is because we try to copy the whole ip/ip6 address to the flow_key,
while we only point the to ip/ip6 saddr. Note that since these are UAPI
headers, __struct_group() is used to avoid the compiler warnings.
Reported-by: kernel test robot <lkp@intel.com>
Fixes: c3f83241 ("net: Add full IPv6 addresses to flow_keys")
Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>
Link: https://lore.kernel.org/r/20221115142400.1204786-1-liuhangbin@gmail.comSigned-off-by: Paolo Abeni <pabeni@redhat.com>

include/net/ip.h

@@ -563,7 +563,7 @@ static inline void iph_to_flow_copy_v4addrs(struct flow_keys *flow,
 	BUILD_BUG_ON(offsetof(typeof(flow->addrs), v4addrs.dst) !=
 		     offsetof(typeof(flow->addrs), v4addrs.src) +
 			      sizeof(flow->addrs.v4addrs.src));
-	memcpy(&flow->addrs.v4addrs, &iph->saddr, sizeof(flow->addrs.v4addrs));
+	memcpy(&flow->addrs.v4addrs, &iph->addrs, sizeof(flow->addrs.v4addrs));
 	flow->control.addr_type = FLOW_DISSECTOR_KEY_IPV4_ADDRS;
 }
 

include/net/ipv6.h

@@ -897,7 +897,7 @@ static inline void iph_to_flow_copy_v6addrs(struct flow_keys *flow,
 	BUILD_BUG_ON(offsetof(typeof(flow->addrs), v6addrs.dst) !=
 		     offsetof(typeof(flow->addrs), v6addrs.src) +
 		     sizeof(flow->addrs.v6addrs.src));
-	memcpy(&flow->addrs.v6addrs, &iph->saddr, sizeof(flow->addrs.v6addrs));
+	memcpy(&flow->addrs.v6addrs, &iph->addrs, sizeof(flow->addrs.v6addrs));
 	flow->control.addr_type = FLOW_DISSECTOR_KEY_IPV6_ADDRS;
 }
 

include/uapi/linux/ip.h

@@ -100,8 +100,10 @@ struct iphdr {
 	__u8	ttl;
 	__u8	protocol;
 	__sum16	check;
+	__struct_group(/* no tag */, addrs, /* no attrs */,
 		__be32	saddr;
 		__be32	daddr;
+	);
 	/*The options start here. */
 };
 

include/uapi/linux/ipv6.h

@@ -130,8 +130,10 @@ struct ipv6hdr {
 	__u8			nexthdr;
 	__u8			hop_limit;
 
+	__struct_group(/* no tag */, addrs, /* no attrs */,
 		struct	in6_addr	saddr;
 		struct	in6_addr	daddr;
+	);
 };