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net: ipv6: support reporting otherwise unknown prefix flags in RTM_NEWPREFIX

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Lorenzo points out that we effectively clear all unknown
flags from PIO when copying them to userspace in the netlink
RTM_NEWPREFIX notification.

We could fix this one at a time as new flags are defined,
or in one fell swoop - I choose the latter.

We could either define 6 new reserved flags (reserved1..6) and handle
them individually (and rename them as new flags are defined), or we
could simply copy the entire unmodified byte over - I choose the latter.

This unfortunately requires some anonymous union/struct magic,
so we add a static assert on the struct size for a little extra safety.

Cc: David Ahern <dsahern@kernel.org>
Cc: Lorenzo Colitti <lorenzo@google.com>
Fixes: 1da177e4c3 ("Linux-2.6.12-rc2")
Signed-off-by: Maciej Żenczykowski <maze@google.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Maciej Żenczykowski 2023-12-06 09:36:12 -08:00 committed by David S. Miller
parent e5dc5afff6
commit bd4a816752
3 changed files with 11 additions and 11 deletions
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12
include/net/addrconf.h
View File

@ -31,17 +31,22 @@ struct prefix_info {
__u8 length;
__u8 prefix_len;
union __packed {
__u8 flags;
struct __packed {
#if defined(__BIG_ENDIAN_BITFIELD)
__u8 onlink : 1,
__u8 onlink : 1,
autoconf : 1,
reserved : 6;
#elif defined(__LITTLE_ENDIAN_BITFIELD)
__u8 reserved : 6,
__u8 reserved : 6,
autoconf : 1,
onlink : 1;
#else
#error "Please fix <asm/byteorder.h>"
#endif
};
};
__be32 valid;
__be32 prefered;
__be32 reserved2;
@ -49,6 +54,9 @@ struct prefix_info {
struct in6_addr prefix;
};
/* rfc4861 4.6.2: IPv6 PIO is 32 bytes in size */
static_assert(sizeof(struct prefix_info) == 32);
#include <linux/ipv6.h>
#include <linux/netdevice.h>
#include <net/if_inet6.h>

4
include/net/if_inet6.h
View File

@ -22,10 +22,6 @@
#define IF_RS_SENT 0x10
#define IF_READY 0x80000000
/* prefix flags */
#define IF_PREFIX_ONLINK 0x01
#define IF_PREFIX_AUTOCONF 0x02
enum {
INET6_IFADDR_STATE_PREDAD,
INET6_IFADDR_STATE_DAD,

6
net/ipv6/addrconf.c
View File

@ -6149,11 +6149,7 @@ static int inet6_fill_prefix(struct sk_buff *skb, struct inet6_dev *idev,
pmsg->prefix_len = pinfo->prefix_len;
pmsg->prefix_type = pinfo->type;
pmsg->prefix_pad3 = 0;
pmsg->prefix_flags = 0;
if (pinfo->onlink)
pmsg->prefix_flags |= IF_PREFIX_ONLINK;
if (pinfo->autoconf)
pmsg->prefix_flags |= IF_PREFIX_AUTOCONF;
pmsg->prefix_flags = pinfo->flags;
if (nla_put(skb, PREFIX_ADDRESS, sizeof(pinfo->prefix), &pinfo->prefix))
goto nla_put_failure;