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-rw-r--r--Documentation/networking/packet_mmap.txt10
-rw-r--r--net/packet/af_packet.c65
2 files changed, 50 insertions, 25 deletions
diff --git a/Documentation/networking/packet_mmap.txt b/Documentation/networking/packet_mmap.txt
index 23dd80e82b8..0f4376ec885 100644
--- a/Documentation/networking/packet_mmap.txt
+++ b/Documentation/networking/packet_mmap.txt
@@ -123,6 +123,16 @@ Transmission process is similar to capture as shown below.
[shutdown] close() --------> destruction of the transmission socket and
deallocation of all associated resources.
+Socket creation and destruction is also straight forward, and is done
+the same way as in capturing described in the previous paragraph:
+
+ int fd = socket(PF_PACKET, mode, 0);
+
+The protocol can optionally be 0 in case we only want to transmit
+via this socket, which avoids an expensive call to packet_rcv().
+In this case, you also need to bind(2) the TX_RING with sll_protocol = 0
+set. Otherwise, htons(ETH_P_ALL) or any other protocol, for example.
+
Binding the socket to your network interface is mandatory (with zero copy) to
know the header size of frames used in the circular buffer.
diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index c503ad6f610..e8b5a0dfca2 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -237,6 +237,30 @@ struct packet_skb_cb {
static void __fanout_unlink(struct sock *sk, struct packet_sock *po);
static void __fanout_link(struct sock *sk, struct packet_sock *po);
+static struct net_device *packet_cached_dev_get(struct packet_sock *po)
+{
+ struct net_device *dev;
+
+ rcu_read_lock();
+ dev = rcu_dereference(po->cached_dev);
+ if (likely(dev))
+ dev_hold(dev);
+ rcu_read_unlock();
+
+ return dev;
+}
+
+static void packet_cached_dev_assign(struct packet_sock *po,
+ struct net_device *dev)
+{
+ rcu_assign_pointer(po->cached_dev, dev);
+}
+
+static void packet_cached_dev_reset(struct packet_sock *po)
+{
+ RCU_INIT_POINTER(po->cached_dev, NULL);
+}
+
/* register_prot_hook must be invoked with the po->bind_lock held,
* or from a context in which asynchronous accesses to the packet
* socket is not possible (packet_create()).
@@ -246,12 +270,10 @@ static void register_prot_hook(struct sock *sk)
struct packet_sock *po = pkt_sk(sk);
if (!po->running) {
- if (po->fanout) {
+ if (po->fanout)
__fanout_link(sk, po);
- } else {
+ else
dev_add_pack(&po->prot_hook);
- rcu_assign_pointer(po->cached_dev, po->prot_hook.dev);
- }
sock_hold(sk);
po->running = 1;
@@ -270,12 +292,11 @@ static void __unregister_prot_hook(struct sock *sk, bool sync)
struct packet_sock *po = pkt_sk(sk);
po->running = 0;
- if (po->fanout) {
+
+ if (po->fanout)
__fanout_unlink(sk, po);
- } else {
+ else
__dev_remove_pack(&po->prot_hook);
- RCU_INIT_POINTER(po->cached_dev, NULL);
- }
__sock_put(sk);
@@ -2048,19 +2069,6 @@ static int tpacket_fill_skb(struct packet_sock *po, struct sk_buff *skb,
return tp_len;
}
-static struct net_device *packet_cached_dev_get(struct packet_sock *po)
-{
- struct net_device *dev;
-
- rcu_read_lock();
- dev = rcu_dereference(po->cached_dev);
- if (dev)
- dev_hold(dev);
- rcu_read_unlock();
-
- return dev;
-}
-
static int tpacket_snd(struct packet_sock *po, struct msghdr *msg)
{
struct sk_buff *skb;
@@ -2077,7 +2085,7 @@ static int tpacket_snd(struct packet_sock *po, struct msghdr *msg)
mutex_lock(&po->pg_vec_lock);
- if (saddr == NULL) {
+ if (likely(saddr == NULL)) {
dev = packet_cached_dev_get(po);
proto = po->num;
addr = NULL;
@@ -2231,7 +2239,7 @@ static int packet_snd(struct socket *sock,
* Get and verify the address.
*/
- if (saddr == NULL) {
+ if (likely(saddr == NULL)) {
dev = packet_cached_dev_get(po);
proto = po->num;
addr = NULL;
@@ -2440,6 +2448,8 @@ static int packet_release(struct socket *sock)
spin_lock(&po->bind_lock);
unregister_prot_hook(sk, false);
+ packet_cached_dev_reset(po);
+
if (po->prot_hook.dev) {
dev_put(po->prot_hook.dev);
po->prot_hook.dev = NULL;
@@ -2495,14 +2505,17 @@ static int packet_do_bind(struct sock *sk, struct net_device *dev, __be16 protoc
spin_lock(&po->bind_lock);
unregister_prot_hook(sk, true);
+
po->num = protocol;
po->prot_hook.type = protocol;
if (po->prot_hook.dev)
dev_put(po->prot_hook.dev);
- po->prot_hook.dev = dev;
+ po->prot_hook.dev = dev;
po->ifindex = dev ? dev->ifindex : 0;
+ packet_cached_dev_assign(po, dev);
+
if (protocol == 0)
goto out_unlock;
@@ -2615,7 +2628,8 @@ static int packet_create(struct net *net, struct socket *sock, int protocol,
po = pkt_sk(sk);
sk->sk_family = PF_PACKET;
po->num = proto;
- RCU_INIT_POINTER(po->cached_dev, NULL);
+
+ packet_cached_dev_reset(po);
sk->sk_destruct = packet_sock_destruct;
sk_refcnt_debug_inc(sk);
@@ -3369,6 +3383,7 @@ static int packet_notifier(struct notifier_block *this, unsigned long msg, void
sk->sk_error_report(sk);
}
if (msg == NETDEV_UNREGISTER) {
+ packet_cached_dev_reset(po);
po->ifindex = -1;
if (po->prot_hook.dev)
dev_put(po->prot_hook.dev);