net/rds/tcp_send.c

Source file repositories/reference/linux-study-clean/net/rds/tcp_send.c

File Facts

System
Linux kernel
Corpus path
net/rds/tcp_send.c
Extension
.c
Size
6961 bytes
Lines
227
Domain
Networking Core
Bucket
Sockets, Protocols, Packet Path, And Network Policy
Inferred role
Networking Core: implementation source
Status
source implementation candidate

Why This File Exists

Networking stack implementation surface: socket APIs, protocol dispatch, packet flow, routing, filtering, and network namespaces.

Dependency Surface

Detected Declarations

Annotated Snippet

if (off == rm->data.op_sg[sg].length) {
			off = 0;
			sg++;
		}
	}

out:
	if (ret <= 0) {
		/* write_space will hit after EAGAIN, all else fatal */
		if (ret == -EAGAIN) {
			rds_tcp_stats_inc(s_tcp_sndbuf_full);
			ret = 0;
		} else {
			/* No need to disconnect/reconnect if path_drop
			 * has already been triggered, because, e.g., of
			 * an incoming RST.
			 */
			if (rds_conn_path_up(cp)) {
				pr_warn("RDS/tcp: send to %pI6c on cp [%d]"
					"returned %d, "
					"disconnecting and reconnecting\n",
					&conn->c_faddr, cp->cp_index, ret);
				rds_conn_path_drop(cp, false);
			}
		}
	}
	if (done == 0)
		done = ret;
	return done;
}

/*
 * rm->m_ack_seq is set to the tcp sequence number that corresponds to the
 * last byte of the message, including the header.  This means that the
 * entire message has been received if rm->m_ack_seq is "before" the next
 * unacked byte of the TCP sequence space.  We have to do very careful
 * wrapping 32bit comparisons here.
 */
int rds_tcp_is_acked(struct rds_message *rm, uint64_t ack)
{
	if (!test_bit(RDS_MSG_HAS_ACK_SEQ, &rm->m_flags))
		return 0;
	return (__s32)((u32)rm->m_ack_seq - (u32)ack) < 0;
}

void rds_tcp_write_space(struct sock *sk)
{
	void (*write_space)(struct sock *sk);
	struct rds_conn_path *cp;
	struct rds_tcp_connection *tc;

	read_lock_bh(&sk->sk_callback_lock);
	cp = sk->sk_user_data;
	if (!cp) {
		write_space = sk->sk_write_space;
		goto out;
	}

	tc = cp->cp_transport_data;
	rdsdebug("write_space for tc %p\n", tc);
	write_space = tc->t_orig_write_space;
	rds_tcp_stats_inc(s_tcp_write_space_calls);

	rdsdebug("tcp una %u\n", rds_tcp_snd_una(tc));
	tc->t_last_seen_una = rds_tcp_snd_una(tc);
	rds_send_path_drop_acked(cp, rds_tcp_snd_una(tc), rds_tcp_is_acked);

	rcu_read_lock();
	if ((refcount_read(&sk->sk_wmem_alloc) << 1) <= sk->sk_sndbuf &&
	    !rds_destroy_pending(cp->cp_conn))
		queue_delayed_work(cp->cp_wq, &cp->cp_send_w, 0);
	rcu_read_unlock();

out:
	read_unlock_bh(&sk->sk_callback_lock);

	/*
	 * write_space is only called when data leaves tcp's send queue if
	 * SOCK_NOSPACE is set.  We set SOCK_NOSPACE every time we put
	 * data in tcp's send queue because we use write_space to parse the
	 * sequence numbers and notice that rds messages have been fully
	 * received.
	 *
	 * tcp's write_space clears SOCK_NOSPACE if the send queue has more
	 * than a certain amount of space. So we need to set it again *after*
	 * we call tcp's write_space or else we might only get called on the
	 * first of a series of incoming tcp acks.
	 */
	write_space(sk);

Annotation

Implementation Notes