netlink: add API to retrieve all group memberships (b42be38b) · Commits · 戴 / test

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>

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;
		}

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