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netlink: allow to listen "all" netns

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More accurately, listen all netns that have a nsid assigned into the netns
where the netlink socket is opened.
For this purpose, a netlink socket option is added:
NETLINK_LISTEN_ALL_NSID. When this option is set on a netlink socket, this
socket will receive netlink notifications from all netns that have a nsid
assigned into the netns where the socket has been opened. The nsid is sent
to userland via an anscillary data.

With this patch, a daemon needs only one socket to listen many netns. This
is useful when the number of netns is high.

Because 0 is a valid value for a nsid, the field nsid_is_set indicates if
the field nsid is valid or not. skb->cb is initialized to 0 on skb
allocation, thus we are sure that we will never send a nsid 0 by error to
the userland.

Signed-off-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Acked-by: Thomas Graf <tgraf@suug.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Nicolas Dichtel 2015-05-07 11:02:53 +02:00 committed by David S. Miller
parent cc3a572fe6
commit 59324cf35a
5 changed files with 61 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
include/linux/netlink.h
View File

@ -28,6 +28,8 @@ struct netlink_skb_parms {
__u32 dst_group;
__u32 flags;
struct sock *sk;
bool nsid_is_set;
int nsid;
};
#define NETLINK_CB(skb) (*(struct netlink_skb_parms*)&((skb)->cb))

2
include/net/net_namespace.h
View File

@ -272,6 +272,8 @@ static inline struct net *read_pnet(const possible_net_t *pnet)
#endif
int peernet2id_alloc(struct net *net, struct net *peer);
int peernet2id(struct net *net, struct net *peer);
bool peernet_has_id(struct net *net, struct net *peer);
struct net *get_net_ns_by_id(struct net *net, int id);
struct pernet_operations {

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

@ -108,6 +108,7 @@ struct nlmsgerr {
#define NETLINK_NO_ENOBUFS 5
#define NETLINK_RX_RING 6
#define NETLINK_TX_RING 7
#define NETLINK_LISTEN_ALL_NSID 8
struct nl_pktinfo {
__u32 group;

10
net/core/net_namespace.c
View File

@ -229,7 +229,7 @@ int peernet2id_alloc(struct net *net, struct net *peer)
EXPORT_SYMBOL(peernet2id_alloc);
/* This function returns, if assigned, the id of a peer netns. */
static int peernet2id(struct net *net, struct net *peer)
int peernet2id(struct net *net, struct net *peer)
{
unsigned long flags;
int id;
@ -240,6 +240,14 @@ static int peernet2id(struct net *net, struct net *peer)
return id;
}
/* This function returns true is the peer netns has an id assigned into the
* current netns.
*/
bool peernet_has_id(struct net *net, struct net *peer)
{
return peernet2id(net, peer) >= 0;
}
struct net *get_net_ns_by_id(struct net *net, int id)
{
unsigned long flags;

52
net/netlink/af_netlink.c
View File

@ -83,6 +83,7 @@ struct listeners {
#define NETLINK_F_RECV_PKTINFO 0x2
#define NETLINK_F_BROADCAST_SEND_ERROR 0x4
#define NETLINK_F_RECV_NO_ENOBUFS 0x8
#define NETLINK_F_LISTEN_ALL_NSID 0x10
static inline int netlink_is_kernel(struct sock *sk)
{
@ -1932,8 +1933,17 @@ static void do_one_broadcast(struct sock *sk,
!test_bit(p->group - 1, nlk->groups))
return;
if (!net_eq(sock_net(sk), p->net))
return;
if (!net_eq(sock_net(sk), p->net)) {
if (!(nlk->flags & NETLINK_F_LISTEN_ALL_NSID))
return;
if (!peernet_has_id(sock_net(sk), p->net))
return;
if (!file_ns_capable(sk->sk_socket->file, p->net->user_ns,
CAP_NET_BROADCAST))
return;
}
if (p->failure) {
netlink_overrun(sk);
@ -1959,13 +1969,22 @@ static void do_one_broadcast(struct sock *sk,
p->failure = 1;
if (nlk->flags & NETLINK_F_BROADCAST_SEND_ERROR)
p->delivery_failure = 1;
} else if (p->tx_filter && p->tx_filter(sk, p->skb2, p->tx_data)) {
goto out;
}
if (p->tx_filter && p->tx_filter(sk, p->skb2, p->tx_data)) {
kfree_skb(p->skb2);
p->skb2 = NULL;
} else if (sk_filter(sk, p->skb2)) {
goto out;
}
if (sk_filter(sk, p->skb2)) {
kfree_skb(p->skb2);
p->skb2 = NULL;
} else if ((val = netlink_broadcast_deliver(sk, p->skb2)) < 0) {
goto out;
}
NETLINK_CB(p->skb2).nsid = peernet2id(sock_net(sk), p->net);
NETLINK_CB(p->skb2).nsid_is_set = true;
val = netlink_broadcast_deliver(sk, p->skb2);
if (val < 0) {
netlink_overrun(sk);
if (nlk->flags & NETLINK_F_BROADCAST_SEND_ERROR)
p->delivery_failure = 1;
@ -1974,6 +1993,7 @@ static void do_one_broadcast(struct sock *sk,
p->delivered = 1;
p->skb2 = NULL;
}
out:
sock_put(sk);
}
@ -2202,6 +2222,16 @@ static int netlink_setsockopt(struct socket *sock, int level, int optname,
break;
}
#endif /* CONFIG_NETLINK_MMAP */
case NETLINK_LISTEN_ALL_NSID:
if (!ns_capable(sock_net(sk)->user_ns, CAP_NET_BROADCAST))
return -EPERM;
if (val)
nlk->flags |= NETLINK_F_LISTEN_ALL_NSID;
else
nlk->flags &= ~NETLINK_F_LISTEN_ALL_NSID;
err = 0;
break;
default:
err = -ENOPROTOOPT;
}
@ -2268,6 +2298,16 @@ static void netlink_cmsg_recv_pktinfo(struct msghdr *msg, struct sk_buff *skb)
put_cmsg(msg, SOL_NETLINK, NETLINK_PKTINFO, sizeof(info), &info);
}
static void netlink_cmsg_listen_all_nsid(struct sock *sk, struct msghdr *msg,
struct sk_buff *skb)
{
if (!NETLINK_CB(skb).nsid_is_set)
return;
put_cmsg(msg, SOL_NETLINK, NETLINK_LISTEN_ALL_NSID, sizeof(int),
&NETLINK_CB(skb).nsid);
}
static int netlink_sendmsg(struct socket *sock, struct msghdr *msg, size_t len)
{
struct sock *sk = sock->sk;
@ -2421,6 +2461,8 @@ static int netlink_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
if (nlk->flags & NETLINK_F_RECV_PKTINFO)
netlink_cmsg_recv_pktinfo(msg, skb);
if (nlk->flags & NETLINK_F_LISTEN_ALL_NSID)
netlink_cmsg_listen_all_nsid(sk, msg, skb);
memset(&scm, 0, sizeof(scm));
scm.creds = *NETLINK_CREDS(skb);