gistfile1.txt

static inline u32 tcp_notsent_lowat(const struct tcp_sock *tp)
{
	struct net *net = sock_net((struct sock *)tp);
	return tp->notsent_lowat ?: net->ipv4.sysctl_tcp_notsent_lowat;
}

static inline bool tcp_stream_memory_free(const struct sock *sk)
{
	const struct tcp_sock *tp = tcp_sk(sk);
	u32 notsent_bytes = tp->write_seq - tp->snd_nxt;

	return notsent_bytes < tcp_notsent_lowat(tp);
}