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net: sk_msg: Simplify sk_psock initialization

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Initializing psock->sk_proto and other saved callbacks is only
done in sk_psock_update_proto, after sk_psock_init has returned.
The logic for this is difficult to follow, and needlessly complex.

Instead, initialize psock->sk_proto whenever we allocate a new
psock. Additionally, assert the following invariants:

* The SK has no ULP: ULP does it's own finagling of sk->sk_prot
* sk_user_data is unused: we need it to store sk_psock

Protect our access to sk_user_data with sk_callback_lock, which
is what other users like reuseport arrays, etc. do.

The result is that an sk_psock is always fully initialized, and
that psock->sk_proto is always the "original" struct proto.
The latter allows us to use psock->sk_proto when initializing
IPv6 TCP / UDP callbacks for sockmap.

Signed-off-by: Lorenz Bauer <lmb@cloudflare.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/bpf/20200821102948.21918-2-lmb@cloudflare.com
This commit is contained in:
Lorenz Bauer
2020-08-21 11:29:43 +01:00
committed by Alexei Starovoitov
parent dca5612f8e
commit 7b219da43f
5 changed files with 41 additions and 46 deletions
Download Patch File Download Diff File Expand all files Collapse all files

13
net/ipv4/tcp_bpf.c
View File

@@ -567,10 +567,9 @@ static void tcp_bpf_rebuild_protos(struct proto prot[TCP_BPF_NUM_CFGS],
prot[TCP_BPF_TX].sendpage = tcp_bpf_sendpage;
}
static void tcp_bpf_check_v6_needs_rebuild(struct sock *sk, struct proto *ops)
static void tcp_bpf_check_v6_needs_rebuild(struct proto *ops)
{
if (sk->sk_family == AF_INET6 &&
unlikely(ops != smp_load_acquire(&tcpv6_prot_saved))) {
if (unlikely(ops != smp_load_acquire(&tcpv6_prot_saved))) {
spin_lock_bh(&tcpv6_prot_lock);
if (likely(ops != tcpv6_prot_saved)) {
tcp_bpf_rebuild_protos(tcp_bpf_prots[TCP_BPF_IPV6], ops);
@@ -603,13 +602,11 @@ struct proto *tcp_bpf_get_proto(struct sock *sk, struct sk_psock *psock)
int family = sk->sk_family == AF_INET6 ? TCP_BPF_IPV6 : TCP_BPF_IPV4;
int config = psock->progs.msg_parser ? TCP_BPF_TX : TCP_BPF_BASE;
if (!psock->sk_proto) {
struct proto *ops = READ_ONCE(sk->sk_prot);
if (tcp_bpf_assert_proto_ops(ops))
if (sk->sk_family == AF_INET6) {
if (tcp_bpf_assert_proto_ops(psock->sk_proto))
return ERR_PTR(-EINVAL);
tcp_bpf_check_v6_needs_rebuild(sk, ops);
tcp_bpf_check_v6_needs_rebuild(psock->sk_proto);
}
return &tcp_bpf_prots[family][config];