* [PATCH v2] netlink: add API to retrieve all group memberships
@ 2015-06-17 15:14 David Herrmann
0 siblings, 0 replies; only message in thread
From: David Herrmann @ 2015-06-17 15:14 UTC (permalink / raw)
To: netdev
Cc: David S. Miller, Thomas Graf, Herbert Xu, linux-kernel,
David Herrmann
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>
---
v2:
- rebase on top of net-next
conflict due to 59324cf35ab ('netlink: allow to listen "all" netns')
include/uapi/linux/netlink.h | 17 +++++++++--------
net/netlink/af_netlink.c | 22 ++++++++++++++++++++++
2 files changed, 31 insertions(+), 8 deletions(-)
diff --git a/include/uapi/linux/netlink.h b/include/uapi/linux/netlink.h
index 3e34b7d..cf6a65c 100644
--- a/include/uapi/linux/netlink.h
+++ b/include/uapi/linux/netlink.h
@@ -101,14 +101,15 @@ struct nlmsgerr {
struct nlmsghdr msg;
};
-#define NETLINK_ADD_MEMBERSHIP 1
-#define NETLINK_DROP_MEMBERSHIP 2
-#define NETLINK_PKTINFO 3
-#define NETLINK_BROADCAST_ERROR 4
-#define NETLINK_NO_ENOBUFS 5
-#define NETLINK_RX_RING 6
-#define NETLINK_TX_RING 7
-#define NETLINK_LISTEN_ALL_NSID 8
+#define NETLINK_ADD_MEMBERSHIP 1
+#define NETLINK_DROP_MEMBERSHIP 2
+#define NETLINK_PKTINFO 3
+#define NETLINK_BROADCAST_ERROR 4
+#define NETLINK_NO_ENOBUFS 5
+#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;
diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index 69d67c3..dea9253 100644
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -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;
}
--
2.4.2
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