linux/net/core/sock_reuseport.c
Paolo Abeni e94a62f507 net/reuseport: drop legacy code
Since commit e32ea7e747 ("soreuseport: fast reuseport UDP socket
selection") and commit c125e80b88 ("soreuseport: fast reuseport
TCP socket selection") the relevant reuseport socket matching the current
packet is selected by the reuseport_select_sock() call. The only
exceptions are invalid BPF filters/filters returning out-of-range
indices.
In the latter case the code implicitly falls back to using the hash
demultiplexing, but instead of selecting the socket inside the
reuseport_select_sock() function, it relies on the hash selection
logic introduced with the early soreuseport implementation.

With this patch, in case of a BPF filter returning a bad socket
index value, we fall back to hash-based selection inside the
reuseport_select_sock() body, so that we can drop some duplicate
code in the ipv4 and ipv6 stack.

This also allows faster lookup in the above scenario and will allow
us to avoid computing the hash value for successful, BPF based
demultiplexing - in a later patch.

Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Acked-by: Craig Gallek <kraig@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2017-11-30 10:56:32 -05:00

267 lines
6.6 KiB
C

// SPDX-License-Identifier: GPL-2.0
/*
* 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. An optional BPF program can also be configured for
* selecting the socket index from the array of available sockets.
*/
#include <net/sock_reuseport.h>
#include <linux/bpf.h>
#include <linux/rcupdate.h>
#define INIT_SOCKS 128
static DEFINE_SPINLOCK(reuseport_lock);
static struct sock_reuseport *__reuseport_alloc(unsigned int max_socks)
{
unsigned int 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;
RCU_INIT_POINTER(reuse->prog, NULL);
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);
/* Allocation attempts can occur concurrently via the setsockopt path
* and the bind/hash path. Nothing to do when we lose the race.
*/
if (rcu_dereference_protected(sk->sk_reuseport_cb,
lockdep_is_held(&reuseport_lock)))
goto out;
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);
out:
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;
more_reuse->prog = reuse->prog;
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);
/* Note: we use kfree_rcu here instead of reuseport_free_rcu so
* that reuse and more_reuse can temporarily share a reference
* to prog.
*/
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, struct sock *sk2)
{
struct sock_reuseport *reuse;
if (!rcu_access_pointer(sk2->sk_reuseport_cb)) {
int err = reuseport_alloc(sk2);
if (err)
return err;
}
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;
}
static void reuseport_free_rcu(struct rcu_head *head)
{
struct sock_reuseport *reuse;
reuse = container_of(head, struct sock_reuseport, rcu);
if (reuse->prog)
bpf_prog_destroy(reuse->prog);
kfree(reuse);
}
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)
call_rcu(&reuse->rcu, reuseport_free_rcu);
break;
}
}
spin_unlock_bh(&reuseport_lock);
}
EXPORT_SYMBOL(reuseport_detach_sock);
static struct sock *run_bpf(struct sock_reuseport *reuse, u16 socks,
struct bpf_prog *prog, struct sk_buff *skb,
int hdr_len)
{
struct sk_buff *nskb = NULL;
u32 index;
if (skb_shared(skb)) {
nskb = skb_clone(skb, GFP_ATOMIC);
if (!nskb)
return NULL;
skb = nskb;
}
/* temporarily advance data past protocol header */
if (!pskb_pull(skb, hdr_len)) {
kfree_skb(nskb);
return NULL;
}
index = bpf_prog_run_save_cb(prog, skb);
__skb_push(skb, hdr_len);
consume_skb(nskb);
if (index >= socks)
return NULL;
return reuse->socks[index];
}
/**
* reuseport_select_sock - Select a socket from an SO_REUSEPORT group.
* @sk: First socket in the group.
* @hash: When no BPF filter is available, use this hash to select.
* @skb: skb to run through BPF filter.
* @hdr_len: BPF filter expects skb data pointer at payload data. If
* the skb does not yet point at the payload, this parameter represents
* how far the pointer needs to advance to reach the payload.
* Returns a socket that should receive the packet (or NULL on error).
*/
struct sock *reuseport_select_sock(struct sock *sk,
u32 hash,
struct sk_buff *skb,
int hdr_len)
{
struct sock_reuseport *reuse;
struct bpf_prog *prog;
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;
prog = rcu_dereference(reuse->prog);
socks = READ_ONCE(reuse->num_socks);
if (likely(socks)) {
/* paired with smp_wmb() in reuseport_add_sock() */
smp_rmb();
if (prog && skb)
sk2 = run_bpf(reuse, socks, prog, skb, hdr_len);
/* no bpf or invalid bpf result: fall back to hash usage */
if (!sk2)
sk2 = reuse->socks[reciprocal_scale(hash, socks)];
}
out:
rcu_read_unlock();
return sk2;
}
EXPORT_SYMBOL(reuseport_select_sock);
struct bpf_prog *
reuseport_attach_prog(struct sock *sk, struct bpf_prog *prog)
{
struct sock_reuseport *reuse;
struct bpf_prog *old_prog;
spin_lock_bh(&reuseport_lock);
reuse = rcu_dereference_protected(sk->sk_reuseport_cb,
lockdep_is_held(&reuseport_lock));
old_prog = rcu_dereference_protected(reuse->prog,
lockdep_is_held(&reuseport_lock));
rcu_assign_pointer(reuse->prog, prog);
spin_unlock_bh(&reuseport_lock);
return old_prog;
}
EXPORT_SYMBOL(reuseport_attach_prog);