tcp_bpf: Charge receive socket buffer in bpf_tcp_ingress()

When bpf_tcp_ingress() is called, the skmsg is being redirected to the
ingress of the destination socket. Therefore, we should charge its
receive socket buffer, instead of sending socket buffer.

Because sk_rmem_schedule() tests pfmemalloc of skb, we need to
introduce a wrapper and call it for skmsg.

Fixes: 604326b ("bpf, sockmap: convert to generic sk_msg interface")
Signed-off-by: Cong Wang <cong.wang@bytedance.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: John Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/bpf/20241210012039.1669389-2-zijianzhang@bytedance.com

Author: Cong Wang

include/net/sock.h

@@ -1527,15 +1527,21 @@ static inline bool sk_wmem_schedule(struct sock *sk, int size)
 }
 
 static inline bool
-sk_rmem_schedule(struct sock *sk, struct sk_buff *skb, int size)
+__sk_rmem_schedule(struct sock *sk, int size, bool pfmemalloc)
 {
 	int delta;
 
 	if (!sk_has_account(sk))
 		return true;
 	delta = size - sk->sk_forward_alloc;
 	return delta <= 0 || __sk_mem_schedule(sk, delta, SK_MEM_RECV) ||
-		skb_pfmemalloc(skb);
+	       pfmemalloc;
+}
+
+static inline bool
+sk_rmem_schedule(struct sock *sk, struct sk_buff *skb, int size)
+{
+	return __sk_rmem_schedule(sk, size, skb_pfmemalloc(skb));
 }
 
 static inline int sk_unused_reserved_mem(const struct sock *sk)

net/ipv4/tcp_bpf.c

@@ -49,7 +49,7 @@ static int bpf_tcp_ingress(struct sock *sk, struct sk_psock *psock,
 		sge = sk_msg_elem(msg, i);
 		size = (apply && apply_bytes < sge->length) ?
 			apply_bytes : sge->length;
-		if (!sk_wmem_schedule(sk, size)) {
+		if (!__sk_rmem_schedule(sk, size, false)) {
 			if (!copied)
 				ret = -ENOMEM;
 			break;