Linux-libre 4.8.2-gnupck-4.8.2-gnu

1 files changed, 65 insertions, 17 deletions

diff --git a/net/ipv4/tcp_timer.c b/net/ipv4/tcp_timer.c
index debdd8b33..f712b411f 100644
--- a/net/ipv4/tcp_timer.c
+++ b/net/ipv4/tcp_timer.c
@@ -24,6 +24,13 @@
 
 int sysctl_tcp_thin_linear_timeouts __read_mostly;
 
+/**
+ *  tcp_write_err() - close socket and save error info
+ *  @sk:  The socket the error has appeared on.
+ *
+ *  Returns: Nothing (void)
+ */
+
 static void tcp_write_err(struct sock *sk)
 {
 	sk->sk_err = sk->sk_err_soft ? : ETIMEDOUT;
@@ -33,16 +40,21 @@ static void tcp_write_err(struct sock *sk)
 	__NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTONTIMEOUT);
 }
 
-/* Do not allow orphaned sockets to eat all our resources.
- * This is direct violation of TCP specs, but it is required
- * to prevent DoS attacks. It is called when a retransmission timeout
- * or zero probe timeout occurs on orphaned socket.
+/**
+ *  tcp_out_of_resources() - Close socket if out of resources
+ *  @sk:        pointer to current socket
+ *  @do_reset:  send a last packet with reset flag
  *
- * Criteria is still not confirmed experimentally and may change.
- * We kill the socket, if:
- * 1. If number of orphaned sockets exceeds an administratively configured
- *    limit.
- * 2. If we have strong memory pressure.
+ *  Do not allow orphaned sockets to eat all our resources.
+ *  This is direct violation of TCP specs, but it is required
+ *  to prevent DoS attacks. It is called when a retransmission timeout
+ *  or zero probe timeout occurs on orphaned socket.
+ *
+ *  Criteria is still not confirmed experimentally and may change.
+ *  We kill the socket, if:
+ *  1. If number of orphaned sockets exceeds an administratively configured
+ *     limit.
+ *  2. If we have strong memory pressure.
  */
 static int tcp_out_of_resources(struct sock *sk, bool do_reset)
 {
@@ -74,7 +86,11 @@ static int tcp_out_of_resources(struct sock *sk, bool do_reset)
 	return 0;
 }
 
-/* Calculate maximal number or retries on an orphaned socket. */
+/**
+ *  tcp_orphan_retries() - Returns maximal number of retries on an orphaned socket
+ *  @sk:    Pointer to the current socket.
+ *  @alive: bool, socket alive state
+ */
 static int tcp_orphan_retries(struct sock *sk, bool alive)
 {
 	int retries = sock_net(sk)->ipv4.sysctl_tcp_orphan_retries; /* May be zero. */
@@ -115,10 +131,22 @@ static void tcp_mtu_probing(struct inet_connection_sock *icsk, struct sock *sk)
 	}
 }
 
-/* This function calculates a "timeout" which is equivalent to the timeout of a
- * TCP connection after "boundary" unsuccessful, exponentially backed-off
+
+/**
+ *  retransmits_timed_out() - returns true if this connection has timed out
+ *  @sk:       The current socket
+ *  @boundary: max number of retransmissions
+ *  @timeout:  A custom timeout value.
+ *             If set to 0 the default timeout is calculated and used.
+ *             Using TCP_RTO_MIN and the number of unsuccessful retransmits.
+ *  @syn_set:  true if the SYN Bit was set.
+ *
+ * The default "timeout" value this function can calculate and use
+ * is equivalent to the timeout of a TCP Connection
+ * after "boundary" unsuccessful, exponentially backed-off
  * retransmissions with an initial RTO of TCP_RTO_MIN or TCP_TIMEOUT_INIT if
  * syn_set flag is set.
+ *
  */
 static bool retransmits_timed_out(struct sock *sk,
 				  unsigned int boundary,
@@ -257,6 +285,16 @@ out:
 		sk_mem_reclaim(sk);
 }
 
+
+/**
+ *  tcp_delack_timer() - The TCP delayed ACK timeout handler
+ *  @data:  Pointer to the current socket. (gets casted to struct sock *)
+ *
+ *  This function gets (indirectly) called when the kernel timer for a TCP packet
+ *  of this socket expires. Calls tcp_delack_timer_handler() to do the actual work.
+ *
+ *  Returns: Nothing (void)
+ */
 static void tcp_delack_timer(unsigned long data)
 {
 	struct sock *sk = (struct sock *)data;
@@ -346,14 +384,23 @@ static void tcp_fastopen_synack_timer(struct sock *sk)
 	 */
 	inet_rtx_syn_ack(sk, req);
 	req->num_timeout++;
+	icsk->icsk_retransmits++;
 	inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
 			  TCP_TIMEOUT_INIT << req->num_timeout, TCP_RTO_MAX);
 }
 
-/*
- *	The TCP retransmit timer.
- */
 
+/**
+ *  tcp_retransmit_timer() - The TCP retransmit timeout handler
+ *  @sk:  Pointer to the current socket.
+ *
+ *  This function gets called when the kernel timer for a TCP packet
+ *  of this socket expires.
+ *
+ *  It handles retransmission, timer adjustment and other necesarry measures.
+ *
+ *  Returns: Nothing (void)
+ */
 void tcp_retransmit_timer(struct sock *sk)
 {
 	struct tcp_sock *tp = tcp_sk(sk);
@@ -494,7 +541,8 @@ out_reset_timer:
 out:;
 }
 
-/* Called with BH disabled */
+/* Called with bottom-half processing disabled.
+   Called by tcp_write_timer() */
 void tcp_write_timer_handler(struct sock *sk)
 {
 	struct inet_connection_sock *icsk = inet_csk(sk);
@@ -539,7 +587,7 @@ static void tcp_write_timer(unsigned long data)
 	if (!sock_owned_by_user(sk)) {
 		tcp_write_timer_handler(sk);
 	} else {
-		/* deleguate our work to tcp_release_cb() */
+		/* delegate our work to tcp_release_cb() */
 		if (!test_and_set_bit(TCP_WRITE_TIMER_DEFERRED, &tcp_sk(sk)->tsq_flags))
 			sock_hold(sk);
 	}