From accf41f8b2b71b03fbd3c7cd5774d44a83874f4a Mon Sep 17 00:00:00 2001 From: Valentin Dornauer Date: Tue, 1 Jul 2014 11:54:00 +0200 Subject: [PATCH] Avoid reusing the same TCP port number Make the initial port number depend on the RTC time. Increase it by 80 for every second, wrapping around after 512 seconds. * grub-core/net/tcp.c (grub_net_tcp_open): Calculate in_port based on RTC time to avoid problems with stale open TCP connections on the remote host. Original patch by Stefan Fritsch . --- ChangeLog | 6 ++++++ grub-core/net/tcp.c | 21 ++++++++++++++++++++- 2 files changed, 26 insertions(+), 1 deletion(-) diff --git a/ChangeLog b/ChangeLog index 5109c5a..61a01d2 100644 --- a/ChangeLog +++ b/ChangeLog @@ -1,3 +1,9 @@ +2014-07-01 Valentin Dornauer + + * grub-core/net/tcp.c (grub_net_tcp_open): Calculate in_port based + on RTC time to avoid problems with stale open TCP connections on the + remote host. + 2014-06-26 Colin Watson * docs/grub-dev.texi (Finding your way around): The build system no diff --git a/grub-core/net/tcp.c b/grub-core/net/tcp.c index 2077f55..b125e6d 100644 --- a/grub-core/net/tcp.c +++ b/grub-core/net/tcp.c @@ -22,6 +22,7 @@ #include #include #include +#include #define TCP_SYN_RETRANSMISSION_TIMEOUT GRUB_NET_INTERVAL #define TCP_SYN_RETRANSMISSION_COUNT GRUB_NET_TRIES @@ -553,13 +554,31 @@ grub_net_tcp_open (char *server, struct grub_net_network_level_interface *inf; grub_net_network_level_address_t gateway; grub_net_tcp_socket_t socket; - static grub_uint16_t in_port = 21550; + static grub_uint16_t in_port = 0; struct grub_net_buff *nb; struct tcphdr *tcph; int i; grub_uint8_t *nbd; grub_net_link_level_address_t ll_target_addr; + if (in_port == 0) + { + struct grub_datetime datetime; + unsigned int seconds; + in_port = 21550; + + /* + * Try to not use the same initial port number on consecutive quick reboots, + * in particular avoid collisions within the usual TIME_WAIT time of 120s. + * Increase the initial port number by 80 for every RTC second mod 512. + * This means the max for in_port is 21550 + 511 * 80 == 62430. + */ + if (grub_get_datetime (&datetime) == 0) + { + seconds = ((datetime.hour * 60 ) + datetime.minute ) * 60 + datetime.second; + in_port += (seconds & 511) * 80; + } + } err = grub_net_resolve_address (server, &addr); if (err) return NULL; -- 1.7.10.4