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Diffstat (limited to 'net/ipv4/tcp_timer.c')
-rw-r--r--net/ipv4/tcp_timer.c81
1 files changed, 64 insertions, 17 deletions
diff --git a/net/ipv4/tcp_timer.c b/net/ipv4/tcp_timer.c
index debdd8b33e69..d84930b2dd95 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;
@@ -350,10 +388,18 @@ static void tcp_fastopen_synack_timer(struct sock *sk)
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 +540,8 @@ 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 +586,7 @@ 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);
}