diff options
Diffstat (limited to 'net/ipv4')
| -rw-r--r-- | net/ipv4/tcp_timer.c | 81 |
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); } |