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authorPatrick McHardy <kaber@trash.net>2013-04-17 06:47:04 +0000
committerDavid S. Miller <davem@davemloft.net>2013-04-19 14:57:58 -0400
commitf9c2288837ba072b21dba955f04a4c97eaa77b1e (patch)
treec02c28e33176fc82b8fd560b3a850351b28617e2 /net/netlink
parent5fd96123ee19b96be7d7b57fd42227e1a146ef05 (diff)
downloadlinux-f9c2288837ba072b21dba955f04a4c97eaa77b1e.tar.gz
netlink: implement memory mapped recvmsg()
Add support for mmap'ed recvmsg(). To allow the kernel to construct messages into the mapped area, a dataless skb is allocated and the data pointer is set to point into the ring frame. This means frames will be delivered to userspace in order of allocation instead of order of transmission. This usually doesn't matter since the order is either not determinable by userspace or message creation/transmission is serialized. The only case where this can have a visible difference is nfnetlink_queue. Userspace can't assume mmap'ed messages have ordered IDs anymore and needs to check this if using batched verdicts. For non-mapped sockets, nothing changes. Signed-off-by: Patrick McHardy <kaber@trash.net> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/netlink')
-rw-r--r--net/netlink/af_netlink.c144
1 files changed, 141 insertions, 3 deletions
diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index 90504a0e42a..d120b5d4d86 100644
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -116,6 +116,11 @@ static bool netlink_skb_is_mmaped(const struct sk_buff *skb)
return NETLINK_CB(skb).flags & NETLINK_SKB_MMAPED;
}
+static bool netlink_rx_is_mmaped(struct sock *sk)
+{
+ return nlk_sk(sk)->rx_ring.pg_vec != NULL;
+}
+
static bool netlink_tx_is_mmaped(struct sock *sk)
{
return nlk_sk(sk)->tx_ring.pg_vec != NULL;
@@ -589,8 +594,54 @@ out:
mutex_unlock(&nlk->pg_vec_lock);
return err;
}
+
+static void netlink_queue_mmaped_skb(struct sock *sk, struct sk_buff *skb)
+{
+ struct nl_mmap_hdr *hdr;
+
+ hdr = netlink_mmap_hdr(skb);
+ hdr->nm_len = skb->len;
+ hdr->nm_group = NETLINK_CB(skb).dst_group;
+ hdr->nm_pid = NETLINK_CB(skb).creds.pid;
+ hdr->nm_uid = NETLINK_CB(skb).creds.uid;
+ hdr->nm_gid = NETLINK_CB(skb).creds.gid;
+ netlink_frame_flush_dcache(hdr);
+ netlink_set_status(hdr, NL_MMAP_STATUS_VALID);
+
+ NETLINK_CB(skb).flags |= NETLINK_SKB_DELIVERED;
+ kfree_skb(skb);
+}
+
+static void netlink_ring_set_copied(struct sock *sk, struct sk_buff *skb)
+{
+ struct netlink_sock *nlk = nlk_sk(sk);
+ struct netlink_ring *ring = &nlk->rx_ring;
+ struct nl_mmap_hdr *hdr;
+
+ spin_lock_bh(&sk->sk_receive_queue.lock);
+ hdr = netlink_current_frame(ring, NL_MMAP_STATUS_UNUSED);
+ if (hdr == NULL) {
+ spin_unlock_bh(&sk->sk_receive_queue.lock);
+ kfree_skb(skb);
+ sk->sk_err = ENOBUFS;
+ sk->sk_error_report(sk);
+ return;
+ }
+ netlink_increment_head(ring);
+ __skb_queue_tail(&sk->sk_receive_queue, skb);
+ spin_unlock_bh(&sk->sk_receive_queue.lock);
+
+ hdr->nm_len = skb->len;
+ hdr->nm_group = NETLINK_CB(skb).dst_group;
+ hdr->nm_pid = NETLINK_CB(skb).creds.pid;
+ hdr->nm_uid = NETLINK_CB(skb).creds.uid;
+ hdr->nm_gid = NETLINK_CB(skb).creds.gid;
+ netlink_set_status(hdr, NL_MMAP_STATUS_COPY);
+}
+
#else /* CONFIG_NETLINK_MMAP */
#define netlink_skb_is_mmaped(skb) false
+#define netlink_rx_is_mmaped(sk) false
#define netlink_tx_is_mmaped(sk) false
#define netlink_mmap sock_no_mmap
#define netlink_poll datagram_poll
@@ -1381,7 +1432,14 @@ static int __netlink_sendskb(struct sock *sk, struct sk_buff *skb)
{
int len = skb->len;
- skb_queue_tail(&sk->sk_receive_queue, skb);
+#ifdef CONFIG_NETLINK_MMAP
+ if (netlink_skb_is_mmaped(skb))
+ netlink_queue_mmaped_skb(sk, skb);
+ else if (netlink_rx_is_mmaped(sk))
+ netlink_ring_set_copied(sk, skb);
+ else
+#endif /* CONFIG_NETLINK_MMAP */
+ skb_queue_tail(&sk->sk_receive_queue, skb);
sk->sk_data_ready(sk, len);
return len;
}
@@ -1492,6 +1550,68 @@ retry:
}
EXPORT_SYMBOL(netlink_unicast);
+struct sk_buff *netlink_alloc_skb(struct sock *ssk, unsigned int size,
+ u32 dst_portid, gfp_t gfp_mask)
+{
+#ifdef CONFIG_NETLINK_MMAP
+ struct sock *sk = NULL;
+ struct sk_buff *skb;
+ struct netlink_ring *ring;
+ struct nl_mmap_hdr *hdr;
+ unsigned int maxlen;
+
+ sk = netlink_getsockbyportid(ssk, dst_portid);
+ if (IS_ERR(sk))
+ goto out;
+
+ ring = &nlk_sk(sk)->rx_ring;
+ /* fast-path without atomic ops for common case: non-mmaped receiver */
+ if (ring->pg_vec == NULL)
+ goto out_put;
+
+ skb = alloc_skb_head(gfp_mask);
+ if (skb == NULL)
+ goto err1;
+
+ spin_lock_bh(&sk->sk_receive_queue.lock);
+ /* check again under lock */
+ if (ring->pg_vec == NULL)
+ goto out_free;
+
+ maxlen = ring->frame_size - NL_MMAP_HDRLEN;
+ if (maxlen < size)
+ goto out_free;
+
+ netlink_forward_ring(ring);
+ hdr = netlink_current_frame(ring, NL_MMAP_STATUS_UNUSED);
+ if (hdr == NULL)
+ goto err2;
+ netlink_ring_setup_skb(skb, sk, ring, hdr);
+ netlink_set_status(hdr, NL_MMAP_STATUS_RESERVED);
+ atomic_inc(&ring->pending);
+ netlink_increment_head(ring);
+
+ spin_unlock_bh(&sk->sk_receive_queue.lock);
+ return skb;
+
+err2:
+ kfree_skb(skb);
+ spin_unlock_bh(&sk->sk_receive_queue.lock);
+err1:
+ sock_put(sk);
+ return NULL;
+
+out_free:
+ kfree_skb(skb);
+ spin_unlock_bh(&sk->sk_receive_queue.lock);
+out_put:
+ sock_put(sk);
+out:
+#endif
+ return alloc_skb(size, gfp_mask);
+}
+EXPORT_SYMBOL_GPL(netlink_alloc_skb);
+
int netlink_has_listeners(struct sock *sk, unsigned int group)
{
int res = 0;
@@ -2270,9 +2390,13 @@ static int netlink_dump(struct sock *sk)
alloc_size = max_t(int, cb->min_dump_alloc, NLMSG_GOODSIZE);
- skb = sock_rmalloc(sk, alloc_size, 0, GFP_KERNEL);
+ if (!netlink_rx_is_mmaped(sk) &&
+ atomic_read(&sk->sk_rmem_alloc) >= sk->sk_rcvbuf)
+ goto errout_skb;
+ skb = netlink_alloc_skb(sk, alloc_size, nlk->portid, GFP_KERNEL);
if (!skb)
goto errout_skb;
+ netlink_skb_set_owner_r(skb, sk);
len = cb->dump(skb, cb);
@@ -2327,6 +2451,19 @@ int __netlink_dump_start(struct sock *ssk, struct sk_buff *skb,
if (cb == NULL)
return -ENOBUFS;
+ /* Memory mapped dump requests need to be copied to avoid looping
+ * on the pending state in netlink_mmap_sendmsg() while the CB hold
+ * a reference to the skb.
+ */
+ if (netlink_skb_is_mmaped(skb)) {
+ skb = skb_copy(skb, GFP_KERNEL);
+ if (skb == NULL) {
+ kfree(cb);
+ return -ENOBUFS;
+ }
+ } else
+ atomic_inc(&skb->users);
+
cb->dump = control->dump;
cb->done = control->done;
cb->nlh = nlh;
@@ -2387,7 +2524,8 @@ void netlink_ack(struct sk_buff *in_skb, struct nlmsghdr *nlh, int err)
if (err)
payload += nlmsg_len(nlh);
- skb = nlmsg_new(payload, GFP_KERNEL);
+ skb = netlink_alloc_skb(in_skb->sk, nlmsg_total_size(payload),
+ NETLINK_CB(in_skb).portid, GFP_KERNEL);
if (!skb) {
struct sock *sk;