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![Martin KaFai Lau](/assets/img/avatar_default.png)
This patch allows a BPF_PROG_TYPE_SK_REUSEPORT bpf prog to select a SO_REUSEPORT sk from a BPF_MAP_TYPE_REUSEPORT_ARRAY introduced in the earlier patch. "bpf_run_sk_reuseport()" will return -ECONNREFUSED when the BPF_PROG_TYPE_SK_REUSEPORT prog returns SK_DROP. The callers, in inet[6]_hashtable.c and ipv[46]/udp.c, are modified to handle this case and return NULL immediately instead of continuing the sk search from its hashtable. It re-uses the existing SO_ATTACH_REUSEPORT_EBPF setsockopt to attach BPF_PROG_TYPE_SK_REUSEPORT. The "sk_reuseport_attach_bpf()" will check if the attaching bpf prog is in the new SK_REUSEPORT or the existing SOCKET_FILTER type and then check different things accordingly. One level of "__reuseport_attach_prog()" call is removed. The "sk_unhashed() && ..." and "sk->sk_reuseport_cb" tests are pushed back to "reuseport_attach_prog()" in sock_reuseport.c. sock_reuseport.c seems to have more knowledge on those test requirements than filter.c. In "reuseport_attach_prog()", after new_prog is attached to reuse->prog, the old_prog (if any) is also directly freed instead of returning the old_prog to the caller and asking the caller to free. The sysctl_optmem_max check is moved back to the "sk_reuseport_attach_filter()" and "sk_reuseport_attach_bpf()". As of other bpf prog types, the new BPF_PROG_TYPE_SK_REUSEPORT is only bounded by the usual "bpf_prog_charge_memlock()" during load time instead of bounded by both bpf_prog_charge_memlock and sysctl_optmem_max. Signed-off-by: Martin KaFai Lau <kafai@fb.com> Acked-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
331 lines
8.4 KiB
C
331 lines
8.4 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* To speed up listener socket lookup, create an array to store all sockets
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* listening on the same port. This allows a decision to be made after finding
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* the first socket. An optional BPF program can also be configured for
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* selecting the socket index from the array of available sockets.
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*/
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#include <net/sock_reuseport.h>
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#include <linux/bpf.h>
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#include <linux/idr.h>
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#include <linux/filter.h>
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#include <linux/rcupdate.h>
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#define INIT_SOCKS 128
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DEFINE_SPINLOCK(reuseport_lock);
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#define REUSEPORT_MIN_ID 1
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static DEFINE_IDA(reuseport_ida);
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int reuseport_get_id(struct sock_reuseport *reuse)
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{
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int id;
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if (reuse->reuseport_id)
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return reuse->reuseport_id;
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id = ida_simple_get(&reuseport_ida, REUSEPORT_MIN_ID, 0,
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/* Called under reuseport_lock */
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GFP_ATOMIC);
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if (id < 0)
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return id;
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reuse->reuseport_id = id;
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return reuse->reuseport_id;
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}
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static struct sock_reuseport *__reuseport_alloc(unsigned int max_socks)
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{
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unsigned int size = sizeof(struct sock_reuseport) +
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sizeof(struct sock *) * max_socks;
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struct sock_reuseport *reuse = kzalloc(size, GFP_ATOMIC);
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if (!reuse)
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return NULL;
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reuse->max_socks = max_socks;
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RCU_INIT_POINTER(reuse->prog, NULL);
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return reuse;
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}
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int reuseport_alloc(struct sock *sk, bool bind_inany)
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{
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struct sock_reuseport *reuse;
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/* bh lock used since this function call may precede hlist lock in
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* soft irq of receive path or setsockopt from process context
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*/
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spin_lock_bh(&reuseport_lock);
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/* Allocation attempts can occur concurrently via the setsockopt path
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* and the bind/hash path. Nothing to do when we lose the race.
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*/
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reuse = rcu_dereference_protected(sk->sk_reuseport_cb,
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lockdep_is_held(&reuseport_lock));
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if (reuse) {
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/* Only set reuse->bind_inany if the bind_inany is true.
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* Otherwise, it will overwrite the reuse->bind_inany
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* which was set by the bind/hash path.
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*/
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if (bind_inany)
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reuse->bind_inany = bind_inany;
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goto out;
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}
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reuse = __reuseport_alloc(INIT_SOCKS);
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if (!reuse) {
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spin_unlock_bh(&reuseport_lock);
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return -ENOMEM;
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}
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reuse->socks[0] = sk;
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reuse->num_socks = 1;
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reuse->bind_inany = bind_inany;
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rcu_assign_pointer(sk->sk_reuseport_cb, reuse);
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out:
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spin_unlock_bh(&reuseport_lock);
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return 0;
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}
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EXPORT_SYMBOL(reuseport_alloc);
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static struct sock_reuseport *reuseport_grow(struct sock_reuseport *reuse)
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{
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struct sock_reuseport *more_reuse;
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u32 more_socks_size, i;
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more_socks_size = reuse->max_socks * 2U;
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if (more_socks_size > U16_MAX)
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return NULL;
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more_reuse = __reuseport_alloc(more_socks_size);
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if (!more_reuse)
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return NULL;
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more_reuse->max_socks = more_socks_size;
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more_reuse->num_socks = reuse->num_socks;
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more_reuse->prog = reuse->prog;
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more_reuse->reuseport_id = reuse->reuseport_id;
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more_reuse->bind_inany = reuse->bind_inany;
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memcpy(more_reuse->socks, reuse->socks,
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reuse->num_socks * sizeof(struct sock *));
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more_reuse->synq_overflow_ts = READ_ONCE(reuse->synq_overflow_ts);
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for (i = 0; i < reuse->num_socks; ++i)
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rcu_assign_pointer(reuse->socks[i]->sk_reuseport_cb,
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more_reuse);
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/* Note: we use kfree_rcu here instead of reuseport_free_rcu so
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* that reuse and more_reuse can temporarily share a reference
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* to prog.
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*/
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kfree_rcu(reuse, rcu);
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return more_reuse;
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}
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static void reuseport_free_rcu(struct rcu_head *head)
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{
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struct sock_reuseport *reuse;
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reuse = container_of(head, struct sock_reuseport, rcu);
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sk_reuseport_prog_free(rcu_dereference_protected(reuse->prog, 1));
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if (reuse->reuseport_id)
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ida_simple_remove(&reuseport_ida, reuse->reuseport_id);
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kfree(reuse);
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}
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/**
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* reuseport_add_sock - Add a socket to the reuseport group of another.
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* @sk: New socket to add to the group.
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* @sk2: Socket belonging to the existing reuseport group.
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* May return ENOMEM and not add socket to group under memory pressure.
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*/
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int reuseport_add_sock(struct sock *sk, struct sock *sk2, bool bind_inany)
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{
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struct sock_reuseport *old_reuse, *reuse;
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if (!rcu_access_pointer(sk2->sk_reuseport_cb)) {
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int err = reuseport_alloc(sk2, bind_inany);
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if (err)
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return err;
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}
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spin_lock_bh(&reuseport_lock);
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reuse = rcu_dereference_protected(sk2->sk_reuseport_cb,
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lockdep_is_held(&reuseport_lock));
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old_reuse = rcu_dereference_protected(sk->sk_reuseport_cb,
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lockdep_is_held(&reuseport_lock));
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if (old_reuse && old_reuse->num_socks != 1) {
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spin_unlock_bh(&reuseport_lock);
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return -EBUSY;
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}
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if (reuse->num_socks == reuse->max_socks) {
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reuse = reuseport_grow(reuse);
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if (!reuse) {
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spin_unlock_bh(&reuseport_lock);
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return -ENOMEM;
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}
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}
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reuse->socks[reuse->num_socks] = sk;
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/* paired with smp_rmb() in reuseport_select_sock() */
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smp_wmb();
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reuse->num_socks++;
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rcu_assign_pointer(sk->sk_reuseport_cb, reuse);
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spin_unlock_bh(&reuseport_lock);
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if (old_reuse)
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call_rcu(&old_reuse->rcu, reuseport_free_rcu);
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return 0;
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}
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void reuseport_detach_sock(struct sock *sk)
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{
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struct sock_reuseport *reuse;
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int i;
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spin_lock_bh(&reuseport_lock);
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reuse = rcu_dereference_protected(sk->sk_reuseport_cb,
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lockdep_is_held(&reuseport_lock));
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/* At least one of the sk in this reuseport group is added to
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* a bpf map. Notify the bpf side. The bpf map logic will
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* remove the sk if it is indeed added to a bpf map.
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*/
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if (reuse->reuseport_id)
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bpf_sk_reuseport_detach(sk);
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rcu_assign_pointer(sk->sk_reuseport_cb, NULL);
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for (i = 0; i < reuse->num_socks; i++) {
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if (reuse->socks[i] == sk) {
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reuse->socks[i] = reuse->socks[reuse->num_socks - 1];
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reuse->num_socks--;
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if (reuse->num_socks == 0)
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call_rcu(&reuse->rcu, reuseport_free_rcu);
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break;
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}
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}
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spin_unlock_bh(&reuseport_lock);
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}
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EXPORT_SYMBOL(reuseport_detach_sock);
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static struct sock *run_bpf_filter(struct sock_reuseport *reuse, u16 socks,
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struct bpf_prog *prog, struct sk_buff *skb,
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int hdr_len)
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{
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struct sk_buff *nskb = NULL;
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u32 index;
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if (skb_shared(skb)) {
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nskb = skb_clone(skb, GFP_ATOMIC);
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if (!nskb)
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return NULL;
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skb = nskb;
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}
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/* temporarily advance data past protocol header */
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if (!pskb_pull(skb, hdr_len)) {
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kfree_skb(nskb);
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return NULL;
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}
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index = bpf_prog_run_save_cb(prog, skb);
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__skb_push(skb, hdr_len);
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consume_skb(nskb);
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if (index >= socks)
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return NULL;
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return reuse->socks[index];
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}
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/**
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* reuseport_select_sock - Select a socket from an SO_REUSEPORT group.
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* @sk: First socket in the group.
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* @hash: When no BPF filter is available, use this hash to select.
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* @skb: skb to run through BPF filter.
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* @hdr_len: BPF filter expects skb data pointer at payload data. If
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* the skb does not yet point at the payload, this parameter represents
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* how far the pointer needs to advance to reach the payload.
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* Returns a socket that should receive the packet (or NULL on error).
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*/
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struct sock *reuseport_select_sock(struct sock *sk,
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u32 hash,
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struct sk_buff *skb,
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int hdr_len)
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{
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struct sock_reuseport *reuse;
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struct bpf_prog *prog;
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struct sock *sk2 = NULL;
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u16 socks;
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rcu_read_lock();
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reuse = rcu_dereference(sk->sk_reuseport_cb);
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/* if memory allocation failed or add call is not yet complete */
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if (!reuse)
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goto out;
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prog = rcu_dereference(reuse->prog);
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socks = READ_ONCE(reuse->num_socks);
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if (likely(socks)) {
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/* paired with smp_wmb() in reuseport_add_sock() */
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smp_rmb();
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if (!prog || !skb)
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goto select_by_hash;
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if (prog->type == BPF_PROG_TYPE_SK_REUSEPORT)
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sk2 = bpf_run_sk_reuseport(reuse, sk, prog, skb, hash);
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else
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sk2 = run_bpf_filter(reuse, socks, prog, skb, hdr_len);
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select_by_hash:
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/* no bpf or invalid bpf result: fall back to hash usage */
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if (!sk2)
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sk2 = reuse->socks[reciprocal_scale(hash, socks)];
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}
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out:
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rcu_read_unlock();
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return sk2;
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}
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EXPORT_SYMBOL(reuseport_select_sock);
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int reuseport_attach_prog(struct sock *sk, struct bpf_prog *prog)
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{
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struct sock_reuseport *reuse;
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struct bpf_prog *old_prog;
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if (sk_unhashed(sk) && sk->sk_reuseport) {
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int err = reuseport_alloc(sk, false);
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if (err)
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return err;
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} else if (!rcu_access_pointer(sk->sk_reuseport_cb)) {
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/* The socket wasn't bound with SO_REUSEPORT */
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return -EINVAL;
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}
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spin_lock_bh(&reuseport_lock);
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reuse = rcu_dereference_protected(sk->sk_reuseport_cb,
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lockdep_is_held(&reuseport_lock));
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old_prog = rcu_dereference_protected(reuse->prog,
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lockdep_is_held(&reuseport_lock));
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rcu_assign_pointer(reuse->prog, prog);
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spin_unlock_bh(&reuseport_lock);
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sk_reuseport_prog_free(old_prog);
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return 0;
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}
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EXPORT_SYMBOL(reuseport_attach_prog);
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