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netlink: add API to retrieve all group memberships

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This patch adds getsockopt(SOL_NETLINK, NETLINK_LIST_MEMBERSHIPS) to
retrieve all groups a socket is a member of. Currently, we have to use
getsockname() and look at the nl.nl_groups bitmask. However, this mask is
limited to 32 groups. Hence, similar to NETLINK_ADD_MEMBERSHIP and
NETLINK_DROP_MEMBERSHIP, this adds a separate sockopt to manager higher
groups IDs than 32.

This new NETLINK_LIST_MEMBERSHIPS option takes a pointer to __u32 and the
size of the array. The array is filled with the full membership-set of the
socket, and the required array size is returned in optlen. Hence,
user-space can retry with a properly sized array in case it was too small.

Signed-off-by: David Herrmann <dh.herrmann@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
David Herrmann 2015-06-17 17:14:33 +02:00 committed by David S. Miller
parent e0df02e0c2
commit b42be38b27
2 changed files with 31 additions and 8 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

1
include/uapi/linux/netlink.h
View file

@ -109,6 +109,7 @@ struct nlmsgerr {
#define NETLINK_RX_RING 6 #define NETLINK_RX_RING 6
#define NETLINK_TX_RING 7 #define NETLINK_TX_RING 7
#define NETLINK_LISTEN_ALL_NSID 8 #define NETLINK_LISTEN_ALL_NSID 8
#define NETLINK_LIST_MEMBERSHIPS 9
struct nl_pktinfo { struct nl_pktinfo {
__u32 group; __u32 group;

22
net/netlink/af_netlink.c
View file

@ -2290,6 +2290,28 @@ static int netlink_getsockopt(struct socket *sock, int level, int optname,
return -EFAULT; return -EFAULT;
err = 0; err = 0;
break; break;
case NETLINK_LIST_MEMBERSHIPS: {
int pos, idx, shift;
err = 0;
netlink_table_grab();
for (pos = 0; pos * 8 < nlk->ngroups; pos += sizeof(u32)) {
if (len - pos < sizeof(u32))
break;
idx = pos / sizeof(unsigned long);
shift = (pos % sizeof(unsigned long)) * 8;
if (put_user((u32)(nlk->groups[idx] >> shift),
(u32 __user *)(optval + pos))) {
err = -EFAULT;
break;
}
}
if (put_user(ALIGN(nlk->ngroups / 8, sizeof(u32)), optlen))
err = -EFAULT;
netlink_table_ungrab();
break;
}
default: default:
err = -ENOPROTOOPT; err = -ENOPROTOOPT;
} }