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: David Herrmann <dh.herrmann@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net>
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@ -109,6 +109,7 @@ struct nlmsgerr {
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#define NETLINK_RX_RING 6
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#define NETLINK_RX_RING 6
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#define NETLINK_TX_RING 7
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#define NETLINK_TX_RING 7
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#define NETLINK_LISTEN_ALL_NSID 8
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#define NETLINK_LISTEN_ALL_NSID 8
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#define NETLINK_LIST_MEMBERSHIPS 9
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struct nl_pktinfo {
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struct nl_pktinfo {
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__u32 group;
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__u32 group;
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@ -2290,6 +2290,28 @@ static int netlink_getsockopt(struct socket *sock, int level, int optname,
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return -EFAULT;
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return -EFAULT;
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err = 0;
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err = 0;
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break;
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break;
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case NETLINK_LIST_MEMBERSHIPS: {
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int pos, idx, shift;
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err = 0;
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netlink_table_grab();
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for (pos = 0; pos * 8 < nlk->ngroups; pos += sizeof(u32)) {
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if (len - pos < sizeof(u32))
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break;
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idx = pos / sizeof(unsigned long);
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shift = (pos % sizeof(unsigned long)) * 8;
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if (put_user((u32)(nlk->groups[idx] >> shift),
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(u32 __user *)(optval + pos))) {
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err = -EFAULT;
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break;
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}
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}
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if (put_user(ALIGN(nlk->ngroups / 8, sizeof(u32)), optlen))
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err = -EFAULT;
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netlink_table_ungrab();
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break;
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}
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default:
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default:
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err = -ENOPROTOOPT;
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err = -ENOPROTOOPT;
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}
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}
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