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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

9
net/ipv4/udp_bpf.c
View File

@@ -22,10 +22,9 @@ static void udp_bpf_rebuild_protos(struct proto *prot, const struct proto *base)
prot->close = sock_map_close;
}
static void udp_bpf_check_v6_needs_rebuild(struct sock *sk, struct proto *ops)
static void udp_bpf_check_v6_needs_rebuild(struct proto *ops)
{
if (sk->sk_family == AF_INET6 &&
unlikely(ops != smp_load_acquire(&udpv6_prot_saved))) {
if (unlikely(ops != smp_load_acquire(&udpv6_prot_saved))) {
spin_lock_bh(&udpv6_prot_lock);
if (likely(ops != udpv6_prot_saved)) {
udp_bpf_rebuild_protos(&udp_bpf_prots[UDP_BPF_IPV6], ops);
@@ -46,8 +45,8 @@ struct proto *udp_bpf_get_proto(struct sock *sk, struct sk_psock *psock)
{
int family = sk->sk_family == AF_INET ? UDP_BPF_IPV4 : UDP_BPF_IPV6;
if (!psock->sk_proto)
udp_bpf_check_v6_needs_rebuild(sk, READ_ONCE(sk->sk_prot));
if (sk->sk_family == AF_INET6)
udp_bpf_check_v6_needs_rebuild(psock->sk_proto);
return &udp_bpf_prots[family];
}