03-18-2006
FreeBSD, fork() and zombies
i'm writing small http proxy server (accept client -> connect to remote proxy server -> recv client's request -> send to remote proxy server -> get responce from remote proxy server -> send answer to client -> close connection to client and to remote proxy server) and having problems with fork(). when connections come to local port, i'm forking them to process the request. but when there are many (100+) simaltenious connections, childs become to work slower and die in 2-20 seconds. i have no limits for simaltenious incoming connections. when child dies it sends SIGCHLD signal to the parent application, which has a handler:
static void sig_chld(int no) {
while (waitpid(-1, NULL, WNOHANG) > 0);
}
and a set up function:
static void install_sig_handlers(void) {
struct sigaction sig_act;
sig_act.sa_handler = sig_chld;
sig_act.sa_flags = 0;
sigfillset(&sig_act.sa_mask);
sigaction(SIGCHLD, &sig_act, NULL);
sig_act.sa_handler = SIG_IGN;
sig_act.sa_flags = 0;
sigemptyset(&sig_act.sa_mask);
sigaction(SIGPIPE, &sig_act, NULL);
}
this works fine on my FreeBSD 4.4 server for 1-100 simaltenious connections from clients. but it becomes wierd when 100+ connections come: zombies start leaving in memory and their number grows. after several minutes of work with 100+ connections server goes down with about 10000 zombies in memory and 0% cpu idle, and at the same time none of my processes (parent or childs) loads the server (by `ps -awx` results) - neither cpu, nor memory.
please help me to find correct decision for this problem. Thanx.
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LEARN ABOUT DEBIAN
connect-proxy
CONNECT-PROXY(1) General Commands Manual CONNECT-PROXY(1)
NAME
connect-proxy -- connect over SOCKS4/5 proxy
SYNOPSIS
connect-proxy [-dnhst45] [-R resolve ] [-p local-port ] [-w secs ] [-H [user@]proxy-server[:port]] ] [-S [user@]socks-server[:port]] ]
[-T proxy-server[:port] ] [-c telnet-proxy-command ] [host] [port]
DESCRIPTION
connect-proxy open connection over SOCKS4/5 proxies
Please, note that any HTTP-Proxy tunnel won't work with content-inspection firewall (unless using SSL).
OPTIONS
-H specifies a hostname and port number of the http proxy server to relay. If port is omitted, 80 is used. You can specify this
value in the environment variable HTTP_PROXY and pass the -h option to use it.
-S specifies the hostname and port number of the SOCKS server to relay. Like -H, port number can be omitted and the default is
1080. You can also specify this value pair in the environment variable SOCKS5_SERVER and give the -s option to use it.
-4 specifies SOCKS relaying and indicates protocol version to use. It is valid only when used with '-s' or '-S'. Default is '-5'
(protocol version 5)
-R method to resolve the hostname. Three keywords ("local", "remote", "both") or dot-notation IP address are acceptable. The key-
word "both" means, "Try local first, then remote". If a dot-notation IP address is specified, use this host as nameserver. The
default is "remote" for SOCKS5 or "local" for others. On SOCKS4 protocol, remote resolving method ("remote" and "both") requires
protocol 4a supported server.
-p will forward a local TCP port instead of using the standard input and output.
-P same to '-p' except keep remote session. The program repeats waiting the port with holding remote session without disconnecting.
To connect the remote session, send EOF to stdin or kill the program.
-w timeout in seconds for making connection with TARGET host.
-d used for debug. If you fail to connect, use this and check request to and response from server.
USAGE
To use proxy, this example is for SOCKS5 connection to connect to "host" at port 25 via SOCKS5 server on "firewall" host.
connect-proxy -S firewall host 25
SOCKS5_SERVER=firewall; export SOCKS5_SERVER; connect-proxy -s host 25
For a HTTP-PROXY connection:
connect-proxy -H proxy-server:8080 host 25
HTTP_PROXY=proxy-server:8080; export HTTP_PROXY; connect-proxy -h host 25
To forward a local port, for example to use ssh:
connect-proxy -p 5550 -H proxy-server:8080 host 22 ssh -l user
To use it along ssh transparently:
# file://~/.ssh/config
# not using proxy on lan
Host 192.*
ProxyCommand connect-proxy %h %p
# mandatory to access the internet
Host *
ProxyCommand connect-proxy -H proxyserver:8080 %h %p
Or for all users ( /etc/ssh/ssh_config )
ENVIRONMENT
SOCKS5_USER, SOCKS5_PASSWORD, HTTP_PROXY_USER, HTTP_PROXY_PASSWORD, CONNECT_PASSWORD, LOGNAME, USER
SEE ALSO
ssh (1).
WWW
http://www.meadowy.org/~gotoh/projects/connect
AUTHOR
This manual page was written by Philippe Coval rzr@gna.org for the Debian system (but may be used by others). Permission is granted to
copy, distribute and/or modify this document under the terms of the GNU General Public License, Version 2 any later version published by
the Free Software Foundation.
On Debian systems, the complete text of the GNU General Public License can be found in /usr/share/common-licenses/GPL.
CONNECT-PROXY(1)