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authorCraig Gallek <kraig@google.com>2016-01-04 17:41:45 -0500
committerDavid S. Miller <davem@davemloft.net>2016-01-04 22:49:58 -0500
commitef456144da8ef507c8cf504284b6042e9201a05c (patch)
treecadc1049482ed0c976bb436c854fec15be5053c2 /net/core/sock_reuseport.c
parentebb3cf41c1a49e334e3fe540ee24a1afb7ed30c4 (diff)
soreuseport: define reuseport groups
struct sock_reuseport is an optional shared structure referenced by each socket belonging to a reuseport group. When a socket is bound to an address/port not yet in use and the reuseport flag has been set, the structure will be allocated and attached to the newly bound socket. When subsequent calls to bind are made for the same address/port, the shared structure will be updated to include the new socket and the newly bound socket will reference the group structure. Usually, when an incoming packet was destined for a reuseport group, all sockets in the same group needed to be considered before a dispatching decision was made. With this structure, an appropriate socket can be found after looking up just one socket in the group. This shared structure will also allow for more complicated decisions to be made when selecting a socket (eg a BPF filter). This work is based off a similar implementation written by Ying Cai <ycai@google.com> for implementing policy-based reuseport selection. Signed-off-by: Craig Gallek <kraig@google.com> Acked-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/core/sock_reuseport.c')
-rw-r--r--net/core/sock_reuseport.c173
1 files changed, 173 insertions, 0 deletions
diff --git a/net/core/sock_reuseport.c b/net/core/sock_reuseport.c
new file mode 100644
index 000000000000..963c8d5f3027
--- /dev/null
+++ b/net/core/sock_reuseport.c
@@ -0,0 +1,173 @@
+/*
+ * To speed up listener socket lookup, create an array to store all sockets
+ * listening on the same port. This allows a decision to be made after finding
+ * the first socket.
+ */
+
+#include <net/sock_reuseport.h>
+#include <linux/rcupdate.h>
+
+#define INIT_SOCKS 128
+
+static DEFINE_SPINLOCK(reuseport_lock);
+
+static struct sock_reuseport *__reuseport_alloc(u16 max_socks)
+{
+ size_t size = sizeof(struct sock_reuseport) +
+ sizeof(struct sock *) * max_socks;
+ struct sock_reuseport *reuse = kzalloc(size, GFP_ATOMIC);
+
+ if (!reuse)
+ return NULL;
+
+ reuse->max_socks = max_socks;
+
+ return reuse;
+}
+
+int reuseport_alloc(struct sock *sk)
+{
+ struct sock_reuseport *reuse;
+
+ /* bh lock used since this function call may precede hlist lock in
+ * soft irq of receive path or setsockopt from process context
+ */
+ spin_lock_bh(&reuseport_lock);
+ WARN_ONCE(rcu_dereference_protected(sk->sk_reuseport_cb,
+ lockdep_is_held(&reuseport_lock)),
+ "multiple allocations for the same socket");
+ reuse = __reuseport_alloc(INIT_SOCKS);
+ if (!reuse) {
+ spin_unlock_bh(&reuseport_lock);
+ return -ENOMEM;
+ }
+
+ reuse->socks[0] = sk;
+ reuse->num_socks = 1;
+ rcu_assign_pointer(sk->sk_reuseport_cb, reuse);
+
+ spin_unlock_bh(&reuseport_lock);
+
+ return 0;
+}
+EXPORT_SYMBOL(reuseport_alloc);
+
+static struct sock_reuseport *reuseport_grow(struct sock_reuseport *reuse)
+{
+ struct sock_reuseport *more_reuse;
+ u32 more_socks_size, i;
+
+ more_socks_size = reuse->max_socks * 2U;
+ if (more_socks_size > U16_MAX)
+ return NULL;
+
+ more_reuse = __reuseport_alloc(more_socks_size);
+ if (!more_reuse)
+ return NULL;
+
+ more_reuse->max_socks = more_socks_size;
+ more_reuse->num_socks = reuse->num_socks;
+
+ memcpy(more_reuse->socks, reuse->socks,
+ reuse->num_socks * sizeof(struct sock *));
+
+ for (i = 0; i < reuse->num_socks; ++i)
+ rcu_assign_pointer(reuse->socks[i]->sk_reuseport_cb,
+ more_reuse);
+
+ kfree_rcu(reuse, rcu);
+ return more_reuse;
+}
+
+/**
+ * reuseport_add_sock - Add a socket to the reuseport group of another.
+ * @sk: New socket to add to the group.
+ * @sk2: Socket belonging to the existing reuseport group.
+ * May return ENOMEM and not add socket to group under memory pressure.
+ */
+int reuseport_add_sock(struct sock *sk, const struct sock *sk2)
+{
+ struct sock_reuseport *reuse;
+
+ spin_lock_bh(&reuseport_lock);
+ reuse = rcu_dereference_protected(sk2->sk_reuseport_cb,
+ lockdep_is_held(&reuseport_lock)),
+ WARN_ONCE(rcu_dereference_protected(sk->sk_reuseport_cb,
+ lockdep_is_held(&reuseport_lock)),
+ "socket already in reuseport group");
+
+ if (reuse->num_socks == reuse->max_socks) {
+ reuse = reuseport_grow(reuse);
+ if (!reuse) {
+ spin_unlock_bh(&reuseport_lock);
+ return -ENOMEM;
+ }
+ }
+
+ reuse->socks[reuse->num_socks] = sk;
+ /* paired with smp_rmb() in reuseport_select_sock() */
+ smp_wmb();
+ reuse->num_socks++;
+ rcu_assign_pointer(sk->sk_reuseport_cb, reuse);
+
+ spin_unlock_bh(&reuseport_lock);
+
+ return 0;
+}
+EXPORT_SYMBOL(reuseport_add_sock);
+
+void reuseport_detach_sock(struct sock *sk)
+{
+ struct sock_reuseport *reuse;
+ int i;
+
+ spin_lock_bh(&reuseport_lock);
+ reuse = rcu_dereference_protected(sk->sk_reuseport_cb,
+ lockdep_is_held(&reuseport_lock));
+ rcu_assign_pointer(sk->sk_reuseport_cb, NULL);
+
+ for (i = 0; i < reuse->num_socks; i++) {
+ if (reuse->socks[i] == sk) {
+ reuse->socks[i] = reuse->socks[reuse->num_socks - 1];
+ reuse->num_socks--;
+ if (reuse->num_socks == 0)
+ kfree_rcu(reuse, rcu);
+ break;
+ }
+ }
+ spin_unlock_bh(&reuseport_lock);
+}
+EXPORT_SYMBOL(reuseport_detach_sock);
+
+/**
+ * reuseport_select_sock - Select a socket from an SO_REUSEPORT group.
+ * @sk: First socket in the group.
+ * @hash: Use this hash to select.
+ * Returns a socket that should receive the packet (or NULL on error).
+ */
+struct sock *reuseport_select_sock(struct sock *sk, u32 hash)
+{
+ struct sock_reuseport *reuse;
+ struct sock *sk2 = NULL;
+ u16 socks;
+
+ rcu_read_lock();
+ reuse = rcu_dereference(sk->sk_reuseport_cb);
+
+ /* if memory allocation failed or add call is not yet complete */
+ if (!reuse)
+ goto out;
+
+ socks = READ_ONCE(reuse->num_socks);
+ if (likely(socks)) {
+ /* paired with smp_wmb() in reuseport_add_sock() */
+ smp_rmb();
+
+ sk2 = reuse->socks[reciprocal_scale(hash, socks)];
+ }
+
+out:
+ rcu_read_unlock();
+ return sk2;
+}
+EXPORT_SYMBOL(reuseport_select_sock);