This patch makes it possible to select a new listener for socket migration by eBPF.
The noteworthy point is that we select a listening socket in reuseport_detach_sock() and reuseport_select_sock(), but we do not have struct skb in the unhash path. Since we cannot pass skb to the eBPF program, we run only the BPF_PROG_TYPE_SK_REUSEPORT program by calling bpf_run_sk_reuseport() with skb NULL. So, some fields derived from skb are also NULL in the eBPF program. Moreover, we can cancel migration by returning SK_DROP. This feature is useful when listeners have different settings at the socket API level or when we want to free resources as soon as possible. Reviewed-by: Benjamin Herrenschmidt <b...@amazon.com> Signed-off-by: Kuniyuki Iwashima <kun...@amazon.co.jp> --- net/core/filter.c | 26 +++++++++++++++++++++----- net/core/sock_reuseport.c | 23 ++++++++++++++++++++--- net/ipv4/inet_hashtables.c | 2 +- 3 files changed, 42 insertions(+), 9 deletions(-) diff --git a/net/core/filter.c b/net/core/filter.c index 01e28f283962..ffc4591878b8 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -8914,6 +8914,22 @@ static u32 xdp_convert_ctx_access(enum bpf_access_type type, SOCK_ADDR_LOAD_NESTED_FIELD_SIZE_OFF(S, NS, F, NF, \ BPF_FIELD_SIZEOF(NS, NF), 0) +#define SOCK_ADDR_LOAD_NESTED_FIELD_SIZE_OFF_OR_NULL(S, NS, F, NF, SIZE, OFF) \ + do { \ + *insn++ = BPF_LDX_MEM(BPF_FIELD_SIZEOF(S, F), si->dst_reg, \ + si->src_reg, offsetof(S, F)); \ + *insn++ = BPF_JMP_IMM(BPF_JEQ, si->dst_reg, 0, 1); \ + *insn++ = BPF_LDX_MEM( \ + SIZE, si->dst_reg, si->dst_reg, \ + bpf_target_off(NS, NF, sizeof_field(NS, NF), \ + target_size) \ + + OFF); \ + } while (0) + +#define SOCK_ADDR_LOAD_NESTED_FIELD_OR_NULL(S, NS, F, NF) \ + SOCK_ADDR_LOAD_NESTED_FIELD_SIZE_OFF_OR_NULL(S, NS, F, NF, \ + BPF_FIELD_SIZEOF(NS, NF), 0) + /* SOCK_ADDR_STORE_NESTED_FIELD_OFF() has semantic similar to * SOCK_ADDR_LOAD_NESTED_FIELD_SIZE_OFF() but for store operation. * @@ -9858,7 +9874,7 @@ static void bpf_init_reuseport_kern(struct sk_reuseport_kern *reuse_kern, reuse_kern->skb = skb; reuse_kern->sk = sk; reuse_kern->selected_sk = NULL; - reuse_kern->data_end = skb->data + skb_headlen(skb); + reuse_kern->data_end = skb ? skb->data + skb_headlen(skb) : NULL; reuse_kern->hash = hash; reuse_kern->reuseport_id = reuse->reuseport_id; reuse_kern->bind_inany = reuse->bind_inany; @@ -10039,10 +10055,10 @@ sk_reuseport_is_valid_access(int off, int size, }) #define SK_REUSEPORT_LOAD_SKB_FIELD(SKB_FIELD) \ - SOCK_ADDR_LOAD_NESTED_FIELD(struct sk_reuseport_kern, \ - struct sk_buff, \ - skb, \ - SKB_FIELD) + SOCK_ADDR_LOAD_NESTED_FIELD_OR_NULL(struct sk_reuseport_kern, \ + struct sk_buff, \ + skb, \ + SKB_FIELD) #define SK_REUSEPORT_LOAD_SK_FIELD(SK_FIELD) \ SOCK_ADDR_LOAD_NESTED_FIELD(struct sk_reuseport_kern, \ diff --git a/net/core/sock_reuseport.c b/net/core/sock_reuseport.c index 74a46197854b..903f78ab35c3 100644 --- a/net/core/sock_reuseport.c +++ b/net/core/sock_reuseport.c @@ -224,6 +224,7 @@ struct sock *reuseport_detach_sock(struct sock *sk) { struct sock_reuseport *reuse; struct sock *nsk = NULL; + struct bpf_prog *prog; int i; spin_lock_bh(&reuseport_lock); @@ -249,8 +250,16 @@ struct sock *reuseport_detach_sock(struct sock *sk) reuse->socks[i] = reuse->socks[reuse->num_socks]; if (reuse->migrate_req) { - if (reuse->num_socks) - nsk = i == reuse->num_socks ? reuse->socks[i - 1] : reuse->socks[i]; + if (reuse->num_socks) { + prog = rcu_dereference(reuse->prog); + if (prog && prog->type == BPF_PROG_TYPE_SK_REUSEPORT) + nsk = bpf_run_sk_reuseport(reuse, sk, prog, + NULL, sk->sk_hash); + + if (!nsk) + nsk = i == reuse->num_socks ? + reuse->socks[i - 1] : reuse->socks[i]; + } reuse->num_closed_socks++; reuse->socks[reuse->max_socks - reuse->num_closed_socks] = sk; @@ -340,8 +349,16 @@ struct sock *reuseport_select_sock(struct sock *sk, /* paired with smp_wmb() in reuseport_add_sock() */ smp_rmb(); - if (!prog || !skb) + if (!prog) + goto select_by_hash; + + if (!skb) { + if (reuse->migrate_req && + prog->type == BPF_PROG_TYPE_SK_REUSEPORT) + sk2 = bpf_run_sk_reuseport(reuse, sk, prog, skb, hash); + goto select_by_hash; + } if (prog->type == BPF_PROG_TYPE_SK_REUSEPORT) sk2 = bpf_run_sk_reuseport(reuse, sk, prog, skb, hash); diff --git a/net/ipv4/inet_hashtables.c b/net/ipv4/inet_hashtables.c index f35c76cf3365..d981e4876679 100644 --- a/net/ipv4/inet_hashtables.c +++ b/net/ipv4/inet_hashtables.c @@ -647,7 +647,7 @@ void inet_unhash(struct sock *sk) if (rcu_access_pointer(sk->sk_reuseport_cb)) { nsk = reuseport_detach_sock(sk); - if (nsk) + if (!IS_ERR_OR_NULL(nsk)) inet_csk_reqsk_queue_migrate(sk, nsk); } -- 2.17.2 (Apple Git-113)