// 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/ip.h>
#include <net/sock_reuseport.h>
#include <linux/bpf.h>
#include <linux/idr.h>
#include <linux/filter.h>
#include <linux/rcupdate.h>
#define INIT_SOCKS 128
DEFINE_SPINLOCK(reuseport_lock);
static DEFINE_IDA(reuseport_ida);
static int reuseport_resurrect(struct sock *sk, struct sock_reuseport *old_reuse,
struct sock_reuseport *reuse, bool bind_inany);
void reuseport_has_conns_set(struct sock *sk)
{
struct sock_reuseport *reuse;
if (!rcu_access_pointer(sk->sk_reuseport_cb))
return;
spin_lock_bh(&reuseport_lock);
reuse = rcu_dereference_protected(sk->sk_reuseport_cb,
lockdep_is_held(&reuseport_lock));
if (likely(reuse))
reuse->has_conns = 1;
spin_unlock_bh(&reuseport_lock);
}
EXPORT_SYMBOL(reuseport_has_conns_set);
static void __reuseport_get_incoming_cpu(struct sock_reuseport *reuse)
{
/* Paired with READ_ONCE() in reuseport_select_sock_by_hash(). */
WRITE_ONCE(reuse->incoming_cpu, reuse->incoming_cpu + 1);
}
static void __reuseport_put_incoming_cpu(struct sock_reuseport *reuse)
{
/* Paired with READ_ONCE() in reuseport_select_sock_by_hash(). */
WRITE_ONCE(reuse->incoming_cpu, reuse->incoming_cpu - 1);
}
static void reuseport_get_incoming_cpu(struct sock *sk, struct sock_reuseport *reuse)
{
if (sk->sk_incoming_cpu >= 0)
__reuseport_get_incoming_cpu(reuse);
}
static void reuseport_put_incoming_cpu(struct sock *sk, struct sock_reuseport *reuse)
{
if (sk->sk_incoming_cpu >= 0)
__reuseport_put_incoming_cpu(reuse);
}
void reuseport_update_incoming_cpu(struct sock *sk, int val)
{
struct sock_reuseport *reuse;
int old_sk_incoming_cpu;
if (unlikely(!rcu_access_pointer(sk->sk_reuseport_cb))) {
/* Paired with REAE_ONCE() in sk_incoming_cpu_update()
* and compute_score().
*/
WRITE_ONCE(sk->sk_incoming_cpu, val);
return;
}
spin_lock_bh(&reuseport_lock);
/* This must be done under reuseport_lock to avoid a race with
* reuseport_grow(), which accesses sk->sk_incoming_cpu without
* lock_sock() when detaching a shutdown()ed sk.
*
* Paired with READ_ONCE() in reuseport_select_sock_by_hash().
*/
old_sk_incoming_cpu = sk->sk_incoming_cpu;
WRITE_ONCE(sk->sk_incoming_cpu, val);
reuse = rcu_dereference_protected(sk->sk_reuseport_cb,
lockdep_is_held(&reuseport_lock));
/* reuseport_grow() has detached a closed sk. */
if (!reuse)
goto out;
if (old_sk_incoming_cpu < 0 && val >= 0)
__reuseport_get_incoming_cpu(reuse);
else if (old_sk_incoming_cpu >= 0 && val < 0)
__reuseport_put_incoming_cpu(reuse);
out:
spin_unlock_bh(&reuseport_lock);
}
static int reuseport_sock_index(struct sock *sk,
const struct sock_reuseport *reuse,
bool closed)
{
int left, right;
if (!closed) {
left = 0;
right = reuse->num_socks;
} else {
left = reuse->max_socks - reuse->num_closed_socks;
right = reuse->max_socks;
}
for (; left < right; left++)
if (reuse->socks[left] == sk)
return left;
return -1;
}
static void __reuseport_add_sock(struct sock *sk,
struct sock_reuseport *reuse)
{
reuse->socks[reuse->num_socks] = sk;
/* paired with smp_rmb() in reuseport_(select|migrate)_sock() */
smp_wmb();
reuse->num_socks++;
reuseport_get_incoming_cpu(sk, reuse);
}
static bool __reuseport_detach_sock(struct sock *sk,
struct sock_reuseport *reuse)
{
int i = reuseport_sock_index(sk, reuse, false);
if (i == -1)
return false;
reuse->socks[i] = reuse->socks[reuse->num_socks - 1];
reuse->num_socks--;
reuseport_put_incoming_cpu(sk, reuse);
return true;
}
static void __reuseport_add_closed_sock(struct sock *sk,
struct sock_reuseport *reuse)
{
reuse->socks[reuse->max_socks - reuse->num_closed_socks - 1] = sk;
/* paired with READ_ONCE() in inet_csk_bind_conflict() */
WRITE_ONCE(reuse->num_closed_socks, reuse->num_closed_socks + 1);
reuseport_get_incoming_cpu(sk, reuse);
}
static bool __reuseport_detach_closed_sock(struct sock *sk,
struct sock_reuseport *reuse)
{
int i = reuseport_sock_index(sk, reuse, true);
if (i == -1)
return false;
reuse->socks[i] = reuse->socks[reuse->max_socks - reuse->num_closed_socks];
/* paired with READ_ONCE() in inet_csk_bind_conflict() */
WRITE_ONCE(reuse->num_closed_socks, reuse->num_closed_socks - 1);
reuseport_put_incoming_cpu(sk, reuse);
return true;
}
static struct sock_reuseport *__reuseport_alloc(unsigned int max_socks)
{
struct sock_reuseport *reuse;
reuse = kzalloc(struct_size(reuse, socks, max_socks), 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, bool bind_inany)
{
struct sock_reuseport *reuse;
int id, ret = 0;
/* 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.
*/
reuse = rcu_dereference_protected(sk->sk_reuseport_cb,
lockdep_is_held(&reuseport_lock));
if (reuse) {
if (reuse->num_closed_socks) {
/* sk was shutdown()ed before */
ret = reuseport_resurrect(sk, reuse, NULL, bind_inany);
goto out;
}
/* Only set reuse->bind_inany if the bind_inany is true.
* Otherwise, it will overwrite the reuse->bind_inany
* which was set by the bind/hash path.
*/
if (bind_inany)
reuse->bind_inany = bind_inany;
goto out;
}
reuse = __reuseport_alloc(INIT_SOCKS);
if (!reuse) {
ret = -ENOMEM;
goto out;
}
id = ida_alloc(&reuseport_ida, GFP_ATOMIC);
if (id < 0) {
kfree(reuse);
ret = id;
goto out;
}
reuse->reuseport_id = id;
reuse->bind_inany = bind_inany;
reuse->socks[0] = sk;
reuse->num_socks = 1;
reuseport_get_incoming_cpu(sk, reuse);
rcu_assign_pointer(sk->sk_reuseport_cb, reuse);
out:
spin_unlock_bh(&reuseport_lock);
return ret;
}
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) {
if (reuse->num_closed_socks) {
/* Make room by removing a closed sk.
* The child has already been migrated.
* Only reqsk left at this point.
*/
struct sock *sk;
sk = reuse->socks[reuse->max_socks - reuse->num_closed_socks];
RCU_INIT_POINTER(sk->sk_reuseport_cb, NULL);
__reuseport_detach_closed_sock(sk, reuse);
return reuse;
}
return NULL;
}
more_reuse = __reuseport_alloc(more_socks_size);
if (!more_reuse)
return NULL;
more_reuse->num_socks = reuse->num_socks;
more_reuse->num_closed_socks = reuse->num_closed_socks;
more_reuse->prog = reuse->prog;
more_reuse->reuseport_id = reuse->reuseport_id;
more_reuse->bind_inany = reuse->bind_inany;
more_reuse->has_conns = reuse->has_conns;
more_reuse->incoming_cpu = reuse->incoming_cpu;
memcpy(more_reuse->socks, reuse->socks,
reuse->num_socks * sizeof(struct sock *));
memcpy(more_reuse->socks +
(more_reuse->max_socks - more_reuse->num_closed_socks),
reuse->socks + (reuse->max_socks - reuse->num_closed_socks),
reuse->num_closed_socks * sizeof(struct sock *));
more_reuse->synq_overflow_ts = READ_ONCE(reuse->synq_overflow_ts);
for (i = 0; i < reuse->max_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;
}
static void reuseport_free_rcu(struct rcu_head *head)
{
struct sock_reuseport *reuse;
reuse = container_of(head, struct sock_reuseport, rcu);
sk_reuseport_prog_free(rcu_dereference_protected(reuse->prog, 1));
ida_free(&reuseport_ida, reuse->reuseport_id);
kfree(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.
* @bind_inany: Whether or not the group is bound to a local INANY address.
*
* May return ENOMEM and not add socket to group under memory pressure.
*/
int reuseport_add_sock(struct sock *sk, struct sock *sk2, bool bind_inany)
{
struct sock_reuseport *old_reuse, *reuse;
if (!rcu_access_pointer(sk2->sk_reuseport_cb)) {
int err = reuseport_alloc(sk2, bind_inany);
if (err)
return err;
}
spin_lock_bh(&reuseport_lock);
reuse = rcu_dereference_protected(sk2->sk_reuseport_cb,
lockdep_is_held(&reuseport_lock));
old_reuse = rcu_dereference_protected(sk->sk_reuseport_cb,
lockdep_is_held(&reuseport_lock));
if (old_reuse && old_reuse->num_closed_socks) {
/* sk was shutdown()ed before */
int err = reuseport_resurrect(sk, old_reuse, reuse, reuse->bind_inany);
spin_unlock_bh(&reuseport_lock);
return err;
}
if (old_reuse && old_reuse->num_socks != 1) {
spin_unlock_bh(&reuseport_lock);
return -EBUSY;
}
if (reuse->num_socks + reuse->num_closed_socks == reuse->max_socks) {
reuse = reuseport_grow(reuse);
if (!reuse) {
spin_unlock_bh(&reuseport_lock);
return -ENOMEM;
}
}
__reuseport_add_sock(sk, reuse);
rcu_assign_pointer(sk->sk_reuseport_cb, reuse);
spin_unlock_bh(&reuseport_lock);
if (old_reuse)
call_rcu(&old_reuse->rcu, reuseport_free_rcu);
return 0;
}
EXPORT_SYMBOL(reuseport_add_sock);
static int reuseport_resurrect(struct sock *sk, struct sock_reuseport *old_reuse,
struct sock_reuseport *reuse, bool bind_inany)
{
if (old_reuse == reuse) {
/* If sk was in the same reuseport group, just pop sk out of
* the closed section and push sk into the listening section.
*/
__reuseport_detach_closed_sock(sk, old_reuse);
__reuseport_add_sock(sk, old_reuse);
return 0;
}
if (!reuse) {
/* In bind()/listen() path, we cannot carry over the eBPF prog
* for the shutdown()ed socket. In setsockopt() path, we should
* not change the eBPF prog of listening sockets by attaching a
* prog to the shutdown()ed socket. Thus, we will allocate a new
* reuseport group and detach sk from the old group.
*/
int id;
reuse = __reuseport_alloc(INIT_SOCKS);
if (!reuse)
return -ENOMEM;
id = ida_alloc(&reuseport_ida, GFP_ATOMIC);
if (id < 0) {
kfree(reuse);
return id;
}
reuse->reuseport_id = id;
reuse->bind_inany = bind_inany;
} else {
/* Move sk from the old group to the new one if
* - all the other listeners in the old group were close()d or
* shutdown()ed, and then sk2 has listen()ed on the same port
* OR
* - sk listen()ed without bind() (or with autobind), was
* shutdown()ed, and then listen()s on another port which
* sk2 listen()s on.
*/
if (reuse->num_socks + reuse->num_closed_socks == reuse->max_socks) {
reuse = reuseport_grow(reuse);
if (!reuse)
return -ENOMEM;
}
}
__reuseport_detach_closed_sock(sk, old_reuse);
__reuseport_add_sock(sk, reuse);
rcu_assign_pointer(sk->sk_reuseport_cb, reuse);
if (old_reuse->num_socks + old_reuse->num_closed_socks == 0)
call_rcu(&old_reuse->rcu, reuseport_free_rcu);
return 0;
}
void reuseport_detach_sock(struct sock *sk)
{
struct sock_reuseport *reuse;
spin_lock_bh(&reuseport_lock);
reuse = rcu_dereference_protected(sk->sk_reuseport_cb,
lockdep_is_held(&reuseport_lock));
/* reuseport_grow() has detached a closed sk */
if (!reuse)
goto out;
/* Notify the bpf side. The sk may be added to a sockarray
* map. If so, sockarray logic will remove it from the map.
*
* Other bpf map types that work with reuseport, like sockmap,
* don't need an explicit callback from here. They override sk
* unhash/close ops to remove the sk from the map before we
* get to this point.
*/
bpf_sk_reuseport_detach(sk);
rcu_assign_pointer(sk->sk_reuseport_cb, NULL);
if (!__reuseport_detach_closed_sock(sk, reuse))
__reuseport_detach_sock(sk, reuse);
if (reuse->num_socks + reuse->num_closed_socks == 0)
call_rcu(&reuse->rcu, reuseport_free_rcu);
out:
spin_unlock_bh(&reuseport_lock);
}
EXPORT_SYMBOL(reuseport_detach_sock);
void reuseport_stop_listen_sock(struct sock *sk)
{
if (sk->sk_protocol == IPPROTO_TCP) {
struct sock_reuseport *reuse;
struct bpf_prog *prog;
spin_lock_bh(&reuseport_lock);
reuse = rcu_dereference_protected(sk->sk_reuseport_cb,
lockdep_is_held(&reuseport_lock));
prog = rcu_dereference_protected(reuse->prog,
lockdep_is_held(&reuseport_lock));
if (READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_migrate_req) ||
(prog && prog->expected_attach_type == BPF_SK_REUSEPORT_SELECT_OR_MIGRATE)) {
/* Migration capable, move sk from the listening section
* to the closed section.
*/
bpf_sk_reuseport_detach(sk);
__reuseport_detach_sock(sk, reuse);
__reuseport_add_closed_sock(sk, reuse);
spin_unlock_bh(&reuseport_lock);
return;
}
spin_unlock_bh(&reuseport_lock);
}
/* Not capable to do migration, detach immediately */
reuseport_detach_sock(sk);
}
EXPORT_SYMBOL(reuseport_stop_listen_sock);
static struct sock *run_bpf_filter(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];
}
static struct sock *reuseport_select_sock_by_hash(struct sock_reuseport *reuse,
u32 hash, u16 num_socks)
{
struct sock *first_valid_sk = NULL;
int i, j;
i = j = reciprocal_scale(hash, num_socks);
do {
struct sock *sk = reuse->socks[i];
if (sk->sk_state != TCP_ESTABLISHED) {
/* Paired with WRITE_ONCE() in __reuseport_(get|put)_incoming_cpu(). */
if (!READ_ONCE(reuse->incoming_cpu))
return sk;
/* Paired with WRITE_ONCE() in reuseport_update_incoming_cpu(). */
if (READ_ONCE(sk->sk_incoming_cpu) == raw_smp_processor_id())
return sk;
if (!first_valid_sk)
first_valid_sk = sk;
}
i++;
if (i >= num_socks)
i = 0;
} while (i != j);
return first_valid_sk;
}
/**
* 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)
goto select_by_hash;
if (prog->type == BPF_PROG_TYPE_SK_REUSEPORT)
sk2 = bpf_run_sk_reuseport(reuse, sk, prog, skb, NULL, hash);
else
sk2 = run_bpf_filter(reuse, socks, prog, skb, hdr_len);
select_by_hash:
/* no bpf or invalid bpf result: fall back to hash usage */
if (!sk2)
sk2 = reuseport_select_sock_by_hash(reuse, hash, socks);
}
out:
rcu_read_unlock();
return sk2;
}
EXPORT_SYMBOL(reuseport_select_sock);
/**
* reuseport_migrate_sock - Select a socket from an SO_REUSEPORT group.
* @sk: close()ed or shutdown()ed socket in the group.
* @migrating_sk: ESTABLISHED/SYN_RECV full socket in the accept queue or
* NEW_SYN_RECV request socket during 3WHS.
* @skb: skb to run through BPF filter.
* Returns a socket (with sk_refcnt +1) that should accept the child socket
* (or NULL on error).
*/
struct sock *reuseport_migrate_sock(struct sock *sk,
struct sock *migrating_sk,
struct sk_buff *skb)
{
struct sock_reuseport *reuse;
struct sock *nsk = NULL;
bool allocated = false;
struct bpf_prog *prog;
u16 socks;
u32 hash;
rcu_read_lock();
reuse = rcu_dereference(sk->sk_reuseport_cb);
if (!reuse)
goto out;
socks = READ_ONCE(reuse->num_socks);
if (unlikely(!socks))
goto failure;
/* paired with smp_wmb() in __reuseport_add_sock() */
smp_rmb();
hash = migrating_sk->sk_hash;
prog = rcu_dereference(reuse->prog);
if (!prog || prog->expected_attach_type != BPF_SK_REUSEPORT_SELECT_OR_MIGRATE) {
if (READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_migrate_req))
goto select_by_hash;
goto failure;
}
if (!skb) {
skb = alloc_skb(0, GFP_ATOMIC);
if (!skb)
goto failure;
allocated = true;
}
nsk = bpf_run_sk_reuseport(reuse, sk, prog, skb, migrating_sk, hash);
if (allocated)
kfree_skb(skb);
select_by_hash:
if (!nsk)
nsk = reuseport_select_sock_by_hash(reuse, hash, socks);
if (IS_ERR_OR_NULL(nsk) || unlikely(!refcount_inc_not_zero(&nsk->sk_refcnt))) {
nsk = NULL;
goto failure;
}
out:
rcu_read_unlock();
return nsk;
failure:
__NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPMIGRATEREQFAILURE);
goto out;
}
EXPORT_SYMBOL(reuseport_migrate_sock);
int reuseport_attach_prog(struct sock *sk, struct bpf_prog *prog)
{
struct sock_reuseport *reuse;
struct bpf_prog *old_prog;
if (sk_unhashed(sk)) {
int err;
if (!sk->sk_reuseport)
return -EINVAL;
err = reuseport_alloc(sk, false);
if (err)
return err;
} else if (!rcu_access_pointer(sk->sk_reuseport_cb)) {
/* The socket wasn't bound with SO_REUSEPORT */
return -EINVAL;
}
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);
sk_reuseport_prog_free(old_prog);
return 0;
}
EXPORT_SYMBOL(reuseport_attach_prog);
int reuseport_detach_prog(struct sock *sk)
{
struct sock_reuseport *reuse;
struct bpf_prog *old_prog;
old_prog = NULL;
spin_lock_bh(&reuseport_lock);
reuse = rcu_dereference_protected(sk->sk_reuseport_cb,
lockdep_is_held(&reuseport_lock));
/* reuse must be checked after acquiring the reuseport_lock
* because reuseport_grow() can detach a closed sk.
*/
if (!reuse) {
spin_unlock_bh(&reuseport_lock);
return sk->sk_reuseport ? -ENOENT : -EINVAL;
}
if (sk_unhashed(sk) && reuse->num_closed_socks) {
spin_unlock_bh(&reuseport_lock);
return -ENOENT;
}
old_prog = rcu_replace_pointer(reuse->prog, old_prog,
lockdep_is_held(&reuseport_lock));
spin_unlock_bh(&reuseport_lock);
if (!old_prog)
return -ENOENT;
sk_reuseport_prog_free(old_prog);
return 0;
}
EXPORT_SYMBOL(reuseport_detach_prog);
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