From 59324cf35aba5336b611074028777838a963d03b Mon Sep 17 00:00:00 2001 From: Nicolas Dichtel Date: Thu, 7 May 2015 11:02:53 +0200 Subject: [PATCH] netlink: allow to listen "all" netns 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 Acked-by: Thomas Graf Signed-off-by: David S. Miller --- include/linux/netlink.h | 2 ++ include/net/net_namespace.h | 2 ++ include/uapi/linux/netlink.h | 1 + net/core/net_namespace.c | 10 ++++++- net/netlink/af_netlink.c | 52 ++++++++++++++++++++++++++++++++---- 5 files changed, 61 insertions(+), 6 deletions(-) diff --git a/include/linux/netlink.h b/include/linux/netlink.h index 6835c1279df7..9120edb650a0 100644 --- a/include/linux/netlink.h +++ b/include/linux/netlink.h @@ -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)) diff --git a/include/net/net_namespace.h b/include/net/net_namespace.h index 6d1e2eae32fb..3f850acc844e 100644 --- a/include/net/net_namespace.h +++ b/include/net/net_namespace.h @@ -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 { diff --git a/include/uapi/linux/netlink.h b/include/uapi/linux/netlink.h index 1a85940f8ab7..3e34b7d702f8 100644 --- a/include/uapi/linux/netlink.h +++ b/include/uapi/linux/netlink.h @@ -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; diff --git a/net/core/net_namespace.c b/net/core/net_namespace.c index ae5008b097de..a665bf490c88 100644 --- a/net/core/net_namespace.c +++ b/net/core/net_namespace.c @@ -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; diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c index bf7f56d7a9aa..a5fff75accf8 100644 --- a/net/netlink/af_netlink.c +++ b/net/netlink/af_netlink.c @@ -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); -- 2.30.2