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Commit b42be38b authored by David Herrmann's avatar David Herrmann Committed by David S. Miller
Browse files

netlink: add API to retrieve all group memberships 



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: default avatarDavid Herrmann <dh.herrmann@gmail.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent e0df02e0

include/uapi/linux/netlink.h

+9 −8
Original line number Diff line number Diff line
@@ -109,6 +109,7 @@ struct nlmsgerr { 
#define NETLINK_RX_RING			6

#define NETLINK_TX_RING			7

#define NETLINK_LISTEN_ALL_NSID		8

#define NETLINK_LIST_MEMBERSHIPS	9



struct nl_pktinfo {

	__u32	group;

net/netlink/af_netlink.c

+22 −0
Original line number Diff line number Diff line
@@ -2290,6 +2290,28 @@ static int netlink_getsockopt(struct socket *sock, int level, int optname, 
			return -EFAULT;

		err = 0;

		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:

		err = -ENOPROTOOPT;

	}