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Files
unrealircd/src/s_bsd.c
T
Bram Matthys 883a5fe413 * The except throttle { } block now also overrides any limitations from
set::max-unknown-connection-per-ip. Useful for WEBIRC/cgiirc gateways.
Reported by KnuX https://bugs.unrealircd.org/view.php?id=5088
2018-09-02 11:40:15 +02:00

1624 lines
41 KiB
C

/*
* Unreal Internet Relay Chat Daemon, src/s_bsd.c
* Copyright (C) 1990 Jarkko Oikarinen and
* University of Oulu, Computing Center
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 1, or (at your option)
* any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
/* -- Jto -- 07 Jul 1990
* Added jlp@hamblin.byu.edu's debugtty fix
*/
/* -- Armin -- Jun 18 1990
* Added setdtablesize() for more socket connections
*/
/* -- Jto -- 13 May 1990
* Added several fixes from msa:
* Better error messages
* Changes in check_access
* Added SO_REUSEADDR fix from zessel@informatik.uni-kl.de
*/
/* 2.78 2/7/94 (C) 1988 University of Oulu, Computing Center and Jarkko Oikarinen */
#ifdef _WIN32
#include <WinSock2.h>
#endif
#include "struct.h"
#include "common.h"
#include "sys.h"
#include "res.h"
#include "numeric.h"
#include "version.h"
#ifndef _WIN32
#include <sys/socket.h>
#include <sys/file.h>
#include <sys/ioctl.h>
#include <sys/resource.h>
#else
#include <io.h>
#endif
#if defined(_SOLARIS)
#include <sys/filio.h>
#endif
#include "inet.h"
#include <stdio.h>
#include <signal.h>
#include <fcntl.h>
#include "sock.h" /* If FD_ZERO isn't define up to this point, */
#include <string.h>
#ifndef _WIN32
#include <netinet/tcp.h>
#endif
#include "proto.h"
/* define it (BSD4.2 needs this) */
#include "h.h"
#include "fdlist.h"
#ifndef IN_LOOPBACKNET
#define IN_LOOPBACKNET 0x7f
#endif
#ifndef _WIN32
#define SET_ERRNO(x) errno = x
#else
#define SET_ERRNO(x) WSASetLastError(x)
#endif /* _WIN32 */
#ifndef SOMAXCONN
# define LISTEN_SIZE (5)
#else
# define LISTEN_SIZE (SOMAXCONN)
#endif
extern char backupbuf[8192];
int OpenFiles = 0; /* GLOBAL - number of files currently open */
int readcalls = 0;
int connect_inet(ConfigItem_link *, aClient *);
void completed_connection(int, int, void *);
void set_sock_opts(int, aClient *, int);
void set_ipv6_opts(int);
void close_listener(ConfigItem_listen *listener);
static char readbuf[BUFSIZE];
char zlinebuf[BUFSIZE];
extern char *version;
extern ircstats IRCstats;
MODVAR TS last_allinuse = 0;
#ifdef USE_LIBCURL
extern void url_do_transfers_async(void);
#endif
/*
* Try and find the correct name to use with getrlimit() for setting the max.
* number of files allowed to be open by this process.
*/
#ifdef RLIMIT_FDMAX
# define RLIMIT_FD_MAX RLIMIT_FDMAX
#else
# ifdef RLIMIT_NOFILE
# define RLIMIT_FD_MAX RLIMIT_NOFILE
# else
# ifdef RLIMIT_OPEN_MAX
# define RLIMIT_FD_MAX RLIMIT_OPEN_MAX
# else
# undef RLIMIT_FD_MAX
# endif
# endif
#endif
void start_of_normal_client_handshake(aClient *acptr);
void proceed_normal_client_handshake(aClient *acptr, struct hostent *he);
/* winlocal */
void close_connections(void)
{
aClient* cptr;
list_for_each_entry(cptr, &lclient_list, lclient_node)
{
if (cptr->fd >= 0)
{
fd_close(cptr->fd);
cptr->fd = -2;
}
}
list_for_each_entry(cptr, &unknown_list, lclient_node)
{
if (cptr->fd >= 0)
{
fd_close(cptr->fd);
cptr->fd = -2;
}
if (cptr->local->authfd >= 0)
{
fd_close(cptr->local->authfd);
cptr->fd = -1;
}
}
close_listeners();
OpenFiles = 0;
#ifdef _WIN32
WSACleanup();
#endif
}
/*
** Cannot use perror() within daemon. stderr is closed in
** ircd and cannot be used. And, worse yet, it might have
** been reassigned to a normal connection...
*/
/*
** report_error
** This a replacement for perror(). Record error to log and
** also send a copy to all *LOCAL* opers online.
**
** text is a *format* string for outputting error. It must
** contain only two '%s', the first will be replaced
** by the sockhost from the cptr, and the latter will
** be taken from strerror(errno).
**
** cptr if not NULL, is the *LOCAL* client associated with
** the error.
*/
void report_error(char *text, aClient *cptr)
{
int errtmp = ERRNO, origerr = ERRNO;
char *host, xbuf[256];
int err, len = sizeof(err), n;
host = (cptr) ? get_client_name(cptr, FALSE) : "";
Debug((DEBUG_ERROR, text, host, STRERROR(errtmp)));
/*
* Get the *real* error from the socket (well try to anyway..).
* This may only work when SO_DEBUG is enabled but its worth the
* gamble anyway.
*/
#ifdef SO_ERROR
if (cptr && !IsMe(cptr) && cptr->fd >= 0)
if (!getsockopt(cptr->fd, SOL_SOCKET, SO_ERROR,
(OPT_TYPE *)&err, &len))
if (err)
errtmp = err;
#endif
if (origerr != errtmp) {
/* Socket error is different than original error,
* some tricks are needed because of 2x strerror() (or at least
* according to the man page) -- Syzop.
*/
snprintf(xbuf, 200, "[syserr='%s'", STRERROR(origerr));
n = strlen(xbuf);
snprintf(xbuf+n, 256-n, ", sockerr='%s']", STRERROR(errtmp));
sendto_snomask(SNO_JUNK, text, host, xbuf);
ircd_log(LOG_ERROR, text, host, xbuf);
} else {
sendto_snomask(SNO_JUNK, text, host, STRERROR(errtmp));
ircd_log(LOG_ERROR, text,host,STRERROR(errtmp));
}
return;
}
void report_baderror(char *text, aClient *cptr)
{
#ifndef _WIN32
int errtmp = errno; /* debug may change 'errno' */
#else
int errtmp = WSAGetLastError(); /* debug may change 'errno' */
#endif
char *host;
int err, len = sizeof(err);
host = (cptr) ? get_client_name(cptr, FALSE) : "";
/* fprintf(stderr, text, host, strerror(errtmp));
fputc('\n', stderr); */
Debug((DEBUG_ERROR, text, host, STRERROR(errtmp)));
/*
* Get the *real* error from the socket (well try to anyway..).
* This may only work when SO_DEBUG is enabled but its worth the
* gamble anyway.
*/
#ifdef SO_ERROR
if (cptr && !IsMe(cptr) && cptr->fd >= 0)
if (!getsockopt(cptr->fd, SOL_SOCKET, SO_ERROR,
(OPT_TYPE *)&err, &len))
if (err)
errtmp = err;
#endif
sendto_umode(UMODE_OPER, text, host, STRERROR(errtmp));
ircd_log(LOG_ERROR, text, host, STRERROR(errtmp));
return;
}
/** Accept an incoming client. */
static void listener_accept(int listener_fd, int revents, void *data)
{
ConfigItem_listen *listener = data;
int cli_fd;
if ((cli_fd = fd_accept(listener->fd)) < 0)
{
if ((ERRNO != P_EWOULDBLOCK) && (ERRNO != P_ECONNABORTED))
{
/* Trouble! accept() returns a strange error.
* Previously in such a case we would just log/broadcast the error and return,
* causing this message to be triggered at a rate of XYZ per second (100% CPU).
* Now we close & re-start the listener.
* Of course the underlying cause of this issue should be investigated, as this
* is very much a workaround.
*/
report_baderror("Cannot accept connections %s:%s", NULL);
sendto_realops("[BUG] Restarting listener on %s:%d due to fatal errors (see previous message)", listener->ip, listener->port);
close_listener(listener);
start_listeners();
}
return;
}
ircstp->is_ac++;
set_sock_opts(cli_fd, NULL, listener->ipv6);
set_non_blocking(cli_fd, NULL);
if ((++OpenFiles >= MAXCLIENTS) || (cli_fd >= MAXCLIENTS))
{
ircstp->is_ref++;
if (last_allinuse < TStime() - 15)
{
sendto_realops("All connections in use. ([@%s/%u])", listener->ip, listener->port);
last_allinuse = TStime();
}
(void)send(cli_fd, "ERROR :All connections in use\r\n", 31, 0);
fd_close(cli_fd);
--OpenFiles;
return;
}
/* add_connection() may fail. we just don't care. */
(void)add_connection(listener, cli_fd);
}
/*
* inetport
*
* Create a socket, bind it to the 'ip' and 'port' and listen to it.
* Returns the fd of the socket created or -1 on error.
*/
int inetport(ConfigItem_listen *listener, char *ip, int port, int ipv6)
{
if (BadPtr(ip))
ip = "*";
if (*ip == '*')
{
if (ipv6)
ip = "::";
else
ip = "0.0.0.0";
}
/* At first, open a new socket */
if (listener->fd >= 0)
abort(); /* Socket already exists but we are asked to create and listen on one. Bad! */
if (port == 0)
abort(); /* Impossible as well, right? */
listener->fd = fd_socket(ipv6 ? AF_INET6 : AF_INET, SOCK_STREAM, 0, "Listener socket");
if (listener->fd < 0)
{
report_baderror("Cannot open stream socket() %s:%s", NULL);
return -1;
}
if (++OpenFiles >= MAXCLIENTS)
{
sendto_ops("No more connections allowed (%s)", listener->ip);
fd_close(listener->fd);
listener->fd = -1;
--OpenFiles;
return -1;
}
set_sock_opts(listener->fd, NULL, ipv6);
set_non_blocking(listener->fd, NULL);
if (!unreal_bind(listener->fd, ip, port, ipv6))
{
ircsnprintf(backupbuf, sizeof(backupbuf), "Error binding stream socket to IP %s port %i",
ip, port);
strlcat(backupbuf, " - %s:%s", sizeof backupbuf);
report_baderror(backupbuf, NULL);
fd_close(listener->fd);
listener->fd = -1;
--OpenFiles;
return -1;
}
if (listen(listener->fd, LISTEN_SIZE) < 0)
{
report_error("listen failed for %s:%s", NULL);
fd_close(listener->fd);
listener->fd = -1;
--OpenFiles;
return -1;
}
#ifdef TCP_DEFER_ACCEPT
if (listener->options & LISTENER_DEFER_ACCEPT)
{
int yes = 1;
(void)setsockopt(listener->fd, IPPROTO_TCP, TCP_DEFER_ACCEPT, &yes, sizeof(int));
}
#endif
#ifdef SO_ACCEPTFILTER
if (listener->options & LISTENER_DEFER_ACCEPT)
{
struct accept_filter_arg afa;
memset(&afa, '\0', sizeof afa);
strlcpy(afa.af_name, "dataready", sizeof afa.af_name);
(void)setsockopt(listener->fd, SOL_SOCKET, SO_ACCEPTFILTER, &afa, sizeof afa);
}
#endif
/* ircd_log(LOG_ERROR, "FD #%d: Listener on %s:%d", listener->fd, ipname, port); */
fd_setselect(listener->fd, FD_SELECT_READ, listener_accept, listener);
return 0;
}
int add_listener2(ConfigItem_listen *conf)
{
if (inetport(conf, conf->ip, conf->port, conf->ipv6))
{
/* This error is already handled upstream:
* ircd_log(LOG_ERROR, "inetport failed for %s:%u", conf->ip, conf->port);
*/
conf->fd = -2;
}
if (conf->fd >= 0)
{
conf->options |= LISTENER_BOUND;
return 1;
}
else
{
conf->fd = -1;
return -1;
}
}
/*
* close_listeners
*
* Close the listener. Note that this won't *free* the listen block, it
* just makes it so no new clients are accepted (and marks the listener
* as "not bound").
*/
void close_listener(ConfigItem_listen *listener)
{
if (listener->fd >= 0)
{
ircd_log(LOG_ERROR, "IRCd no longer listening on %s:%d (%s)%s",
listener->ip, listener->port,
listener->ipv6 ? "IPv6" : "IPv4",
listener->options & LISTENER_SSL ? " (SSL)" : "");
fd_close(listener->fd);
--OpenFiles;
}
listener->options &= ~LISTENER_BOUND;
listener->fd = -1;
if (listener->ssl_ctx)
{
SSL_CTX_free(listener->ssl_ctx);
listener->ssl_ctx = NULL;
}
}
void close_listeners(void)
{
aClient *cptr;
ConfigItem_listen *aconf, *aconf_next;
/* close all 'extra' listening ports we have */
for (aconf = conf_listen; aconf != NULL; aconf = aconf_next)
{
aconf_next = aconf->next;
if (aconf->flag.temporary)
close_listener(aconf);
}
}
/*
* init_sys
*/
void init_sys(void)
{
int fd, i;
#ifdef RLIMIT_FD_MAX
struct rlimit limit;
if (!getrlimit(RLIMIT_FD_MAX, &limit))
{
if (limit.rlim_max < MAXCONNECTIONS)
{
(void)fprintf(stderr, "The OS enforces a limit on max open files\n");
#ifndef LONG_LONG_RLIM_T
(void)fprintf(stderr, "Hard Limit: %ld MAXCONNECTIONS: %d\n",
#else
(void)fprintf(stderr, "Hard Limit: %lld MAXCONNECTIONS: %d\n",
#endif
limit.rlim_max, MAXCONNECTIONS);
(void)fprintf(stderr, "Fix MAXCONNECTIONS\n");
exit(-1);
}
limit.rlim_cur = limit.rlim_max; /* make soft limit the max */
if (setrlimit(RLIMIT_FD_MAX, &limit) == -1)
{
/* HACK: if it's mac os X then don't error... */
#ifndef OSXTIGER
#ifndef LONG_LONG_RLIM_T
(void)fprintf(stderr, "error setting max fd's to %ld\n",
#else
(void)fprintf(stderr, "error setting max fd's to %lld\n",
#endif
limit.rlim_cur);
exit(-1);
#endif // OSXTIGER
}
}
#endif // RLIMIT_FD_MAX
#ifndef _WIN32
#ifdef BACKEND_SELECT
if (MAXCONNECTIONS > FD_SETSIZE)
{
fprintf(stderr, "MAXCONNECTIONS (%d) is higher than FD_SETSIZE (%d)\n", MAXCONNECTIONS, FD_SETSIZE);
fprintf(stderr, "You might need to recompile the IRCd, or if you're running Linux, read the release notes\n");
exit(-1);
}
#endif
#endif
/* Create new session / set process group */
#if defined(HPUX) || defined(_SOLARIS) || \
defined(_POSIX_SOURCE) || defined(SVR4) || defined(SGI) || \
defined(OSXTIGER) || defined(__QNX__)
(void)setsid();
#elif !defined(_WIN32)
(void)setpgrp(0, (int)getpid());
#endif
init_resolver(1);
return;
}
/** Replace a file descriptor (*NIX only).
* @param oldfd: the old FD to close and re-use
* @param name: descriptive string of the old fd, eg: "stdin".
* @param mode: an open() mode, such as O_WRONLY.
*/
void replacefd(int oldfd, char *name, int mode)
{
#ifndef _WIN32
int newfd = open("/dev/null", mode);
if (newfd < 0)
{
fprintf(stderr, "Warning: could not open /dev/null\n");
return;
}
if (oldfd < 0)
{
fprintf(stderr, "Warning: could not replace %s (invalid fd)\n", name);
return;
}
if (dup2(newfd, oldfd) < 0)
{
fprintf(stderr, "Warning: could not replace %s (dup2 error)\n", name);
return;
}
#endif
}
/* Mass close standard file descriptors.
* We used to really just close them here (or in init_sys() actually),
* making the fd's available for other purposes such as internet sockets.
* For safety we now dup2() them to /dev/null. This in case someone
* accidentally does a fprintf(stderr,..) somewhere in the code or some
* library outputs error messages to stderr (such as libc with heap
* errors). We don't want any IRC client to receive such a thing!
*/
void close_std_descriptors(void)
{
#if !defined(_WIN32) && !defined(NOCLOSEFD)
replacefd(fileno(stdin), "stdin", O_RDONLY);
replacefd(fileno(stdout), "stdout", O_WRONLY);
replacefd(fileno(stderr), "stderr", O_WRONLY);
#endif
}
void write_pidfile(void)
{
#ifdef IRCD_PIDFILE
int fd;
char buff[20];
if ((fd = open(conf_files->pid_file, O_CREAT | O_WRONLY, 0600)) >= 0)
{
bzero(buff, sizeof(buff));
(void)ircsnprintf(buff, sizeof(buff), "%5d\n", (int)getpid());
if (write(fd, buff, strlen(buff)) == -1)
Debug((DEBUG_NOTICE, "Error writing to pid file %s",
conf_files->pid_file));
(void)close(fd);
return;
}
#ifdef DEBUGMODE
else
Debug((DEBUG_NOTICE, "Error opening pid file %s",
conf_files->pid_file));
#endif
#endif
}
/** Reject an insecure (outgoing) server link that isn't SSL/TLS.
* This function is void and not int because it can be called from other void functions
*/
void reject_insecure_server(aClient *cptr)
{
sendto_umode(UMODE_OPER, "Could not link with server %s with SSL/TLS enabled. "
"Please check logs on the other side of the link and make sure the other IRCd "
"is compiled with SSL support enabled. "
"If you insist with insecure linking then you can set link::options::outgoing::insecure",
cptr->name);
dead_link(cptr, "Rejected link without SSL/TLS");
}
void start_server_handshake(aClient *cptr)
{
ConfigItem_link *aconf = cptr->serv ? cptr->serv->conf : NULL;
if (!aconf)
{
/* Should be impossible. */
sendto_ops("Lost configuration for %s in start_server_handshake()", get_client_name(cptr, FALSE));
return;
}
RunHook(HOOKTYPE_SERVER_HANDSHAKE_OUT, cptr);
sendto_one(cptr, "PASS :%s", (aconf->auth->type == AUTHTYPE_PLAINTEXT) ? aconf->auth->data : "*");
send_protoctl_servers(cptr, 0);
send_proto(cptr, aconf);
if (NEW_LINKING_PROTOCOL)
{
/* Sending SERVER message moved to m_protoctl, so it's send after the first PROTOCTL
* we receive from the remote server. Of course, this assumes that the remote server
* to which we are connecting will at least send one PROTOCTL... but since it's an
* outgoing connect, we can safely assume it's a remote UnrealIRCd server (or some
* other advanced server..). -- Syzop
*/
/* Use this nasty hack, to make 3.2.9<->pre-3.2.9 linking work */
sendto_one(cptr, "__PANGPANG__");
} else {
send_server_message(cptr);
}
}
/*
** completed_connection
** Complete non-blocking connect()-sequence. Check access and
** terminate connection, if trouble detected.
**
** Return TRUE, if successfully completed
** FALSE, if failed and ClientExit
*/
void completed_connection(int fd, int revents, void *data)
{
aClient *cptr = data;
ConfigItem_link *aconf = cptr->serv ? cptr->serv->conf : NULL;
if (IsHandshake(cptr))
{
/* Due to delayed ircd_SSL_connect call */
start_server_handshake(cptr);
fd_setselect(fd, FD_SELECT_READ, read_packet, cptr);
return;
}
SetHandshake(cptr);
if (!aconf)
{
sendto_ops("Lost configuration for %s", get_client_name(cptr, FALSE));
return;
}
if (!cptr->local->ssl && !(aconf->outgoing.options & CONNECT_INSECURE))
{
sendto_one(cptr, "STARTTLS");
} else
{
start_server_handshake(cptr);
}
if (!IsDead(cptr))
start_auth(cptr);
fd_setselect(fd, FD_SELECT_READ, read_packet, cptr);
}
/*
** close_connection
** Close the physical connection. This function must make
** MyConnect(cptr) == FALSE, and set cptr->from == NULL.
*/
void close_connection(aClient *cptr)
{
ConfigItem_link *aconf;
#ifdef DO_REMAPPING
int i, j;
int empty = cptr->fd;
#endif
if (IsServer(cptr))
{
ircstp->is_sv++;
ircstp->is_sbs += cptr->local->sendB;
ircstp->is_sbr += cptr->local->receiveB;
ircstp->is_sks += cptr->local->sendK;
ircstp->is_skr += cptr->local->receiveK;
ircstp->is_sti += TStime() - cptr->local->firsttime;
if (ircstp->is_sbs > 1023)
{
ircstp->is_sks += (ircstp->is_sbs >> 10);
ircstp->is_sbs &= 0x3ff;
}
if (ircstp->is_sbr > 1023)
{
ircstp->is_skr += (ircstp->is_sbr >> 10);
ircstp->is_sbr &= 0x3ff;
}
}
else if (IsClient(cptr))
{
ircstp->is_cl++;
ircstp->is_cbs += cptr->local->sendB;
ircstp->is_cbr += cptr->local->receiveB;
ircstp->is_cks += cptr->local->sendK;
ircstp->is_ckr += cptr->local->receiveK;
ircstp->is_cti += TStime() - cptr->local->firsttime;
if (ircstp->is_cbs > 1023)
{
ircstp->is_cks += (ircstp->is_cbs >> 10);
ircstp->is_cbs &= 0x3ff;
}
if (ircstp->is_cbr > 1023)
{
ircstp->is_ckr += (ircstp->is_cbr >> 10);
ircstp->is_cbr &= 0x3ff;
}
}
else
ircstp->is_ni++;
/*
* remove outstanding DNS queries.
*/
unrealdns_delreq_bycptr(cptr);
if (cptr->local->authfd >= 0)
{
fd_close(cptr->local->authfd);
cptr->local->authfd = -1;
--OpenFiles;
}
if (cptr->fd >= 0)
{
send_queued(cptr);
if (IsSSL(cptr) && cptr->local->ssl) {
SSL_set_shutdown(cptr->local->ssl, SSL_RECEIVED_SHUTDOWN);
SSL_smart_shutdown(cptr->local->ssl);
SSL_free(cptr->local->ssl);
cptr->local->ssl = NULL;
}
fd_close(cptr->fd);
cptr->fd = -2;
--OpenFiles;
DBufClear(&cptr->local->sendQ);
DBufClear(&cptr->local->recvQ);
}
cptr->from = NULL; /* ...this should catch them! >:) --msa */
return;
}
void set_ipv6_opts(int fd)
{
#if defined(IPV6_V6ONLY)
int opt = 1;
(void)setsockopt(fd, IPPROTO_IPV6, IPV6_V6ONLY, (OPT_TYPE *)&opt, sizeof(opt));
#endif
}
/*
** set_sock_opts
*/
void set_sock_opts(int fd, aClient *cptr, int ipv6)
{
int opt;
if (ipv6)
set_ipv6_opts(fd);
#ifdef SO_REUSEADDR
opt = 1;
if (setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, (OPT_TYPE *)&opt,
sizeof(opt)) < 0)
report_error("setsockopt(SO_REUSEADDR) %s:%s", cptr);
#endif
#if defined(SO_DEBUG) && defined(DEBUGMODE) && 0
/* Solaris with SO_DEBUG writes to syslog by default */
#if !defined(_SOLARIS) || defined(HAVE_SYSLOG)
opt = 1;
if (setsockopt(fd, SOL_SOCKET, SO_DEBUG, (OPT_TYPE *)&opt,
sizeof(opt)) < 0)
report_error("setsockopt(SO_DEBUG) %s:%s", cptr);
#endif /* _SOLARIS */
#endif
#if defined(SO_USELOOPBACK) && !defined(_WIN32)
opt = 1;
if (setsockopt(fd, SOL_SOCKET, SO_USELOOPBACK, (OPT_TYPE *)&opt,
sizeof(opt)) < 0)
report_error("setsockopt(SO_USELOOPBACK) %s:%s", cptr);
#endif
#ifdef SO_RCVBUF
opt = 8192;
if (setsockopt(fd, SOL_SOCKET, SO_RCVBUF, (OPT_TYPE *)&opt,
sizeof(opt)) < 0)
report_error("setsockopt(SO_RCVBUF) %s:%s", cptr);
#endif
#ifdef SO_SNDBUF
# ifdef _SEQUENT_
/* seems that Sequent freezes up if the receving buffer is a different size
* to the sending buffer (maybe a tcp window problem too).
*/
opt = 8192;
# else
opt = 8192;
# endif
if (setsockopt(fd, SOL_SOCKET, SO_SNDBUF, (OPT_TYPE *)&opt,
sizeof(opt)) < 0)
report_error("setsockopt(SO_SNDBUF) %s:%s", cptr);
#endif
}
int get_sockerr(aClient *cptr)
{
#ifndef _WIN32
int errtmp = errno, err = 0, len = sizeof(err);
#else
int errtmp = WSAGetLastError(), err = 0, len = sizeof(err);
#endif
#ifdef SO_ERROR
if (cptr->fd >= 0)
if (!getsockopt(cptr->fd, SOL_SOCKET, SO_ERROR,
(OPT_TYPE *)&err, &len))
if (err)
errtmp = err;
#endif
return errtmp;
}
/*
* set_blocking - Set the client connection into non-blocking mode.
* If your system doesn't support this, you're screwed, ircd will run like
* crap.
* returns true (1) if successful, false (0) otherwise
*/
int set_blocking(int fd)
{
int flags;
#ifdef _WIN32
int nonb;
#endif
#ifndef _WIN32
if ((flags = fcntl(fd, F_GETFL, 0)) < 0
|| fcntl(fd, F_SETFL, flags & ~O_NONBLOCK) < 0)
#else
nonb = 0;
if (ioctlsocket(fd, FIONBIO, &nonb) < 0)
#endif
return 0;
else
return 1;
}
/*
** set_non_blocking
** Set the client connection into non-blocking mode. If your
** system doesn't support this, you can make this a dummy
** function (and get all the old problems that plagued the
** blocking version of IRC--not a problem if you are a
** lightly loaded node...)
*/
void set_non_blocking(int fd, aClient *cptr)
{
int res, nonb = 0;
/*
** NOTE: consult ALL your relevant manual pages *BEFORE* changing
** these ioctl's. There are quite a few variations on them,
** as can be seen by the PCS one. They are *NOT* all the same.
** Heed this well. - Avalon.
*/
#ifdef NBLOCK_POSIX
nonb |= O_NONBLOCK;
#endif
#ifdef NBLOCK_BSD
nonb |= O_NDELAY;
#endif
#ifdef NBLOCK_SYSV
/* This portion of code might also apply to NeXT. -LynX */
res = 1;
if (ioctl(fd, FIONBIO, &res) < 0)
{
if (cptr)
report_error("ioctl(fd,FIONBIO) failed for %s:%s", cptr);
}
#else
# if !defined(_WIN32)
if ((res = fcntl(fd, F_GETFL, 0)) == -1)
{
if (cptr)
{
report_error("fcntl(fd, F_GETFL) failed for %s:%s", cptr);
}
}
else if (fcntl(fd, F_SETFL, res | nonb) == -1)
{
if (cptr)
{
report_error("fcntl(fd, F_SETL, nonb) failed for %s:%s", cptr);
}
}
# else
nonb = 1;
if (ioctlsocket(fd, FIONBIO, &nonb) < 0)
{
if (cptr)
{
report_error("ioctlsocket(fd,FIONBIO) failed for %s:%s", cptr);
}
}
# endif
#endif
return;
}
/** Returns 1 if using a loopback IP (127.0.0.1) or
* using a local IP number on the same machine (effectively the same;
* no network traffic travels outside this machine).
*/
int is_loopback_ip(char *ip)
{
ConfigItem_listen *e;
if (!strcmp(ip, "127.0.0.1") || !strcmp(ip, "0:0:0:0:0:0:0:1") || !strcmp(ip, "0:0:0:0:0:ffff:127.0.0.1"))
return 1;
for (e = conf_listen; e; e = e->next)
{
if ((e->options & LISTENER_BOUND) && !strcmp(ip, e->ip))
return 1;
}
return 0;
}
char *getpeerip(aClient *acptr, int fd, int *port)
{
static char ret[HOSTLEN+1];
if (IsIPV6(acptr))
{
struct sockaddr_in6 addr;
int len = sizeof(addr);
if (getpeername(fd, (struct sockaddr *)&addr, &len) < 0)
return NULL;
*port = ntohs(addr.sin6_port);
return inetntop(AF_INET6, &addr.sin6_addr.s6_addr, ret, sizeof(ret));
} else
{
struct sockaddr_in addr;
int len = sizeof(addr);
if (getpeername(fd, (struct sockaddr *)&addr, &len) < 0)
return NULL;
*port = ntohs(addr.sin_port);
return inetntop(AF_INET, &addr.sin_addr.s_addr, ret, sizeof(ret));
}
}
/*
* Creates a client which has just connected to us on the given fd.
* The sockhost field is initialized with the ip# of the host.
* The client is added to the linked list of clients but isnt added to any
* hash tables yuet since it doesnt have a name.
*/
aClient *add_connection(ConfigItem_listen *listener, int fd)
{
aClient *acptr, *acptr2;
ConfigItem_ban *bconf;
int i, j;
char *ip;
int port = 0;
acptr = make_client(NULL, &me);
/* If listener is IPv6 then mark client (acptr) as IPv6 */
if (listener->ipv6)
SetIPV6(acptr);
ip = getpeerip(acptr, fd, &port);
if (!ip)
{
/* On Linux 2.4 and FreeBSD the socket may just have been disconnected
* so it's not a serious error and can happen quite frequently -- Syzop
*/
if (ERRNO != P_ENOTCONN)
{
report_error("Failed to accept new client %s :%s", acptr);
}
add_con_refuse:
ircstp->is_ref++;
acptr->fd = -2;
free_client(acptr);
fd_close(fd);
--OpenFiles;
return NULL;
}
/* Fill in sockhost & ip ASAP */
set_sockhost(acptr, ip);
acptr->ip = strdup(ip);
acptr->local->port = port;
/* Tag loopback connections as FLAGS_LOCAL */
if (is_loopback_ip(acptr->ip))
{
ircstp->is_loc++;
acptr->flags |= FLAGS_LOCAL;
}
j = 1;
if (!Find_except(acptr, CONF_EXCEPT_THROTTLE))
{
list_for_each_entry(acptr2, &unknown_list, lclient_node)
{
if (!strcmp(acptr->ip,GetIP(acptr2)))
{
j++;
if (j > iConf.max_unknown_connections_per_ip)
{
ircsnprintf(zlinebuf, sizeof(zlinebuf),
"ERROR :Closing Link: [%s] (Too many unknown connections from your IP)"
"\r\n",
acptr->ip);
(void)send(fd, zlinebuf, strlen(zlinebuf), 0);
goto add_con_refuse;
}
}
}
}
if ((bconf = Find_ban(acptr, acptr->ip, CONF_BAN_IP)))
{
if (bconf)
{
ircsnprintf(zlinebuf, sizeof(zlinebuf),
"ERROR :Closing Link: [%s] (You are not welcome on "
"this server: %s. Email %s for more information.)\r\n",
acptr->ip,
bconf->reason ? bconf->reason : "no reason",
KLINE_ADDRESS);
(void)send(fd, zlinebuf, strlen(zlinebuf), 0);
goto add_con_refuse;
}
}
else if (find_tkline_match_zap(acptr) != -1)
{
(void)send(fd, zlinebuf, strlen(zlinebuf), 0);
goto add_con_refuse;
}
else
{
int val;
if (!(val = throttle_can_connect(acptr)))
{
ircsnprintf(zlinebuf, sizeof(zlinebuf),
"ERROR :Closing Link: [%s] (Throttled: Reconnecting too fast) -"
"Email %s for more information.\r\n",
acptr->ip,
KLINE_ADDRESS);
(void)send(fd, zlinebuf, strlen(zlinebuf), 0);
goto add_con_refuse;
}
else if (val == 1)
add_throttling_bucket(acptr);
}
acptr->fd = fd;
acptr->local->listener = listener;
if (acptr->local->listener != NULL)
acptr->local->listener->clients++;
add_client_to_list(acptr);
IRCstats.unknown++;
acptr->status = STAT_UNKNOWN;
list_add(&acptr->lclient_node, &unknown_list);
if ((listener->options & LISTENER_SSL) && ctx_server)
{
SSL_CTX *ctx = listener->ssl_ctx ? listener->ssl_ctx : ctx_server;
if (ctx)
{
SetSSLAcceptHandshake(acptr);
Debug((DEBUG_DEBUG, "Starting SSL accept handshake for %s", acptr->local->sockhost));
if ((acptr->local->ssl = SSL_new(ctx)) == NULL)
{
goto add_con_refuse;
}
acptr->flags |= FLAGS_SSL;
SSL_set_fd(acptr->local->ssl, fd);
SSL_set_nonblocking(acptr->local->ssl);
SSL_set_ex_data(acptr->local->ssl, ssl_client_index, acptr);
if (!ircd_SSL_accept(acptr, fd)) {
Debug((DEBUG_DEBUG, "Failed SSL accept handshake in instance 1: %s", acptr->local->sockhost));
SSL_set_shutdown(acptr->local->ssl, SSL_RECEIVED_SHUTDOWN);
SSL_smart_shutdown(acptr->local->ssl);
SSL_free(acptr->local->ssl);
goto add_con_refuse;
}
}
}
else
start_of_normal_client_handshake(acptr);
return acptr;
}
static int dns_special_flag = 0; /* This is for an "interesting" race condition very ugly. */
void start_of_normal_client_handshake(aClient *acptr)
{
struct hostent *he;
acptr->status = STAT_UNKNOWN; /* reset, to be sure (SSL handshake has ended) */
RunHook(HOOKTYPE_HANDSHAKE, acptr);
if (!DONT_RESOLVE)
{
if (SHOWCONNECTINFO && !acptr->serv && !IsServersOnlyListener(acptr->local->listener))
sendto_one(acptr, "%s", REPORT_DO_DNS);
dns_special_flag = 1;
he = unrealdns_doclient(acptr);
dns_special_flag = 0;
if (acptr->local->hostp)
goto doauth; /* Race condition detected, DNS has been done, continue with auth */
if (!he)
{
/* Resolving in progress */
SetDNS(acptr);
} else {
/* Host was in our cache */
acptr->local->hostp = he;
if (SHOWCONNECTINFO && !acptr->serv && !IsServersOnlyListener(acptr->local->listener))
sendto_one(acptr, "%s", REPORT_FIN_DNSC);
}
}
doauth:
start_auth(acptr);
fd_setselect(acptr->fd, FD_SELECT_READ, read_packet, acptr);
}
void proceed_normal_client_handshake(aClient *acptr, struct hostent *he)
{
ClearDNS(acptr);
acptr->local->hostp = he;
if (SHOWCONNECTINFO && !acptr->serv && !IsServersOnlyListener(acptr->local->listener))
sendto_one(acptr, "%s", acptr->local->hostp ? REPORT_FIN_DNS : REPORT_FAIL_DNS);
if (!dns_special_flag && !DoingAuth(acptr))
finish_auth(acptr);
}
/*
** read_packet
**
** Read a 'packet' of data from a connection and process it. Read in 8k
** chunks to give a better performance rating (for server connections).
** Do some tricky stuff for client connections to make sure they don't do
** any flooding >:-) -avalon
** If 'doread' is set to 0 then we don't actually read (no recv()),
** however we still check if we need to dequeue anything from the recvQ.
** This is necessary, since we may have put something on the recvQ due
** to fake lag. -- Syzop
** With new I/O code, things work differently. Surprise!
** read_one_packet() reads packets in and dumps them as quickly as
** possible into the client's DBuf. Then we parse data out of the DBuf,
** after we're done reading crap.
** -- nenolod
*/
static int parse_client_queued(aClient *cptr)
{
int dolen = 0;
int allow_read;
int done;
time_t now = TStime();
char buf[BUFSIZE];
if (DoingDNS(cptr))
return 0; /* we delay processing of data until the host is resolved */
if (DoingAuth(cptr))
return 0; /* we delay processing of data until identd has replied */
if (!IsPerson(cptr) && !IsServer(cptr) && (iConf.handshake_delay > 0) &&
(TStime() - cptr->local->firsttime < iConf.handshake_delay))
{
return 0; /* we delay processing of data until set::handshake-delay is reached */
}
while (DBufLength(&cptr->local->recvQ) &&
((cptr->status < STAT_UNKNOWN) || (cptr->local->since - now < 10)))
{
dolen = dbuf_getmsg(&cptr->local->recvQ, buf);
if (dolen == 0)
return 0;
if (dopacket(cptr, buf, dolen) == FLUSH_BUFFER)
return FLUSH_BUFFER;
}
return 0;
}
int process_packet(aClient *cptr, char *readbuf, int length, int killsafely)
{
dbuf_put(&cptr->local->recvQ, readbuf, length);
/* parse some of what we have (inducing fakelag, etc) */
if (parse_client_queued(cptr) == FLUSH_BUFFER)
return 0;
/* flood from unknown connection */
if (IsUnknown(cptr) && (DBufLength(&cptr->local->recvQ) > UNKNOWN_FLOOD_AMOUNT*1024))
{
sendto_snomask(SNO_FLOOD, "Flood from unknown connection %s detected",
cptr->local->sockhost);
if (!killsafely)
ban_flooder(cptr);
else
dead_link(cptr, "Flood from unknown connection");
return 0;
}
/* excess flood check */
if (IsPerson(cptr) && DBufLength(&cptr->local->recvQ) > get_recvq(cptr))
{
sendto_snomask(SNO_FLOOD,
"*** Flood -- %s!%s@%s (%d) exceeds %d recvQ",
cptr->name[0] ? cptr->name : "*",
cptr->user ? cptr->user->username : "*",
cptr->user ? cptr->user->realhost : "*",
DBufLength(&cptr->local->recvQ), get_recvq(cptr));
if (!killsafely)
exit_client(cptr, cptr, cptr, "Excess Flood");
else
dead_link(cptr, "Excess Flood");
return 0;
}
return 1;
}
void read_packet(int fd, int revents, void *data)
{
aClient *cptr = data;
int length = 0;
time_t now = TStime();
Hook *h;
int processdata;
/* Don't read from dead sockets */
if (IsDead(cptr))
{
fd_setselect(fd, FD_SELECT_READ, NULL, cptr);
return;
}
SET_ERRNO(0);
fd_setselect(fd, FD_SELECT_READ, read_packet, cptr);
fd_setselect(fd, FD_SELECT_WRITE, NULL, cptr);
while (1)
{
if (IsSSL(cptr) && cptr->local->ssl != NULL)
{
length = SSL_read(cptr->local->ssl, readbuf, sizeof(readbuf));
if (length < 0)
{
int err = SSL_get_error(cptr->local->ssl, length);
switch (err)
{
case SSL_ERROR_WANT_WRITE:
fd_setselect(fd, FD_SELECT_READ, NULL, cptr);
fd_setselect(fd, FD_SELECT_WRITE, read_packet, cptr);
length = -1;
SET_ERRNO(P_EWOULDBLOCK);
break;
case SSL_ERROR_WANT_READ:
fd_setselect(fd, FD_SELECT_READ, read_packet, cptr);
fd_setselect(fd, FD_SELECT_WRITE, NULL, cptr);
length = -1;
SET_ERRNO(P_EWOULDBLOCK);
break;
case SSL_ERROR_SYSCALL:
break;
case SSL_ERROR_SSL:
if (ERRNO == P_EAGAIN)
break;
default:
/*length = 0;
SET_ERRNO(0);
^^ why this? we should error. -- todo: is errno correct?
*/
break;
}
}
}
else
length = recv(cptr->fd, readbuf, sizeof(readbuf), 0);
if (length <= 0)
{
if (length < 0 && (ERRNO == P_EWOULDBLOCK || ERRNO == P_EAGAIN || ERRNO == P_EINTR))
return;
if (IsServer(cptr) || cptr->serv) /* server or outgoing connection */
sendto_umode_global(UMODE_OPER, "Lost connection to %s: Read error",
get_client_name(cptr, FALSE));
exit_client(cptr, cptr, cptr, "Read error");
return;
}
cptr->local->lasttime = now;
if (cptr->local->lasttime > cptr->local->since)
cptr->local->since = cptr->local->lasttime;
cptr->flags &= ~(FLAGS_PINGSENT | FLAGS_NONL);
processdata = 1;
for (h = Hooks[HOOKTYPE_RAWPACKET_IN]; h; h = h->next)
{
processdata = (*(h->func.intfunc))(cptr, readbuf, &length);
if (processdata < 0)
return;
}
if (processdata && !process_packet(cptr, readbuf, length, 0))
return;
/* bail on short read! */
if (length < sizeof(readbuf))
return;
}
}
/* Process input from clients that may have been deliberately delayed due to fake lag */
void process_clients(void)
{
aClient *cptr;
/* Problem:
* 1) When 'cptr' exits we can't check 'current_element->next' since this
* has been freed.
* 2) We can't use list_for_each_entry_safe() which would take care of #1
* (like if 'cptr' exited). This is because it would set
* next = current_element->next, however parse_client_queued may
* potentially kill 'next' (eg /KILL user) so then we would follow
* an invalid pointer.
* So I'm just re-running the loop. We could use some kind of 'tagging'
* to mark already processed clients, however parse_client_queued() already
* takes care not to read (fake) lagged up clients, and we don't actually
* read/recv anything, so clients in the beginning of the list won't
* benefit/get higher prio.
* Another alternative is not to run the loop again, but that WOULD be
* unfair to clients later in the list which wouldn't be processed then
* under a heavy (kill) load scenario.
* I think the chosen solution is best, though it remains silly. -- Syzop
*/
do {
list_for_each_entry(cptr, &lclient_list, lclient_node)
if ((cptr->fd >= 0) && DBufLength(&cptr->local->recvQ))
if (parse_client_queued(cptr) == FLUSH_BUFFER)
break;
} while(&cptr->lclient_node != &lclient_list);
/* For unknown_list we also have to take into account the unknown->client transition */
do {
list_for_each_entry(cptr, &unknown_list, lclient_node)
if ((cptr->fd >= 0) && DBufLength(&cptr->local->recvQ))
if ((parse_client_queued(cptr) == FLUSH_BUFFER) || (cptr->status > STAT_UNKNOWN))
break;
} while(&cptr->lclient_node != &unknown_list);
}
/* When auth is finished, go back and parse all prior input. */
void finish_auth(aClient *acptr)
{
SetAccess(acptr);
}
/** Returns 4 if 'str' is a valid IPv4 address
* and 6 if 'str' is a valid IPv6 IP address.
* Zero (0) is returned in any other case (eg: hostname).
*/
int is_valid_ip(char *str)
{
char scratch[64];
if (inet_pton(AF_INET, str, scratch) == 1)
return 4; /* IPv4 */
if (inet_pton(AF_INET6, str, scratch) == 1)
return 6; /* IPv6 */
return 0; /* not an IP address */
}
/*
* connect_server
*/
int connect_server(ConfigItem_link *aconf, aClient *by, struct hostent *hp)
{
aClient *cptr;
char *s;
#ifdef DEBUGMODE
sendto_realops("connect_server() called with aconf %p, refcount: %d, TEMP: %s",
aconf, aconf->refcount, aconf->flag.temporary ? "YES" : "NO");
#endif
if (!aconf->outgoing.hostname)
return -1; /* This is an incoming-only link block. Caller shouldn't call us. */
if (!hp)
{
/* Remove "cache" */
safefree(aconf->connect_ip);
}
/*
* If we dont know the IP# for this host and itis a hostname and
* not a ip# string, then try and find the appropriate host record.
*/
if (!aconf->connect_ip)
{
if (is_valid_ip(aconf->outgoing.hostname))
{
/* link::outgoing::hostname is an IP address. No need to resolve host. */
aconf->connect_ip = strdup(aconf->outgoing.hostname);
} else
{
/* It's a hostname, let the resolver look it up. */
int ipv4_explicit_bind = 0;
if (aconf->outgoing.bind_ip && (is_valid_ip(aconf->outgoing.bind_ip) == 4))
ipv4_explicit_bind = 1;
/* We need this 'aconf->refcount++' or else there's a race condition between
* starting resolving the host and the result of the resolver (we could
* REHASH in that timeframe) leading to an invalid (freed!) 'aconf'.
* -- Syzop, bug #0003689.
*/
aconf->refcount++;
unrealdns_gethostbyname_link(aconf->outgoing.hostname, aconf, ipv4_explicit_bind);
return -2;
}
}
cptr = make_client(NULL, &me);
cptr->local->hostp = hp;
/*
* Copy these in so we have something for error detection.
*/
strlcpy(cptr->name, aconf->servername, sizeof(cptr->name));
strlcpy(cptr->local->sockhost, aconf->outgoing.hostname, HOSTLEN + 1);
if (!connect_inet(aconf, cptr))
{
int errtmp = ERRNO;
report_error("Connect to host %s failed: %s", cptr);
if (by && IsPerson(by) && !MyClient(by))
sendto_one(by,
":%s NOTICE %s :*** Connect to host %s failed.",
me.name, by->name, cptr->name);
fd_close(cptr->fd);
--OpenFiles;
cptr->fd = -2;
free_client(cptr);
SET_ERRNO(errtmp);
if (ERRNO == P_EINTR)
SET_ERRNO(P_ETIMEDOUT);
return -1;
}
/* The socket has been connected or connect is in progress. */
(void)make_server(cptr);
cptr->serv->conf = aconf;
cptr->serv->conf->refcount++;
#ifdef DEBUGMODE
sendto_realops("connect_server() CONTINUED (%s:%d), aconf %p, refcount: %d, TEMP: %s",
__FILE__, __LINE__, aconf, aconf->refcount, aconf->flag.temporary ? "YES" : "NO");
#endif
Debug((DEBUG_ERROR, "reference count for %s (%s) is now %d",
cptr->name, cptr->serv->conf->servername, cptr->serv->conf->refcount));
if (by && IsPerson(by))
{
(void)strlcpy(cptr->serv->by, by->name, sizeof cptr->serv->by);
if (cptr->serv->user)
free_user(cptr->serv->user, NULL);
cptr->serv->user = by->user;
by->user->refcnt++;
}
else
{
(void)strlcpy(cptr->serv->by, "AutoConn.", sizeof cptr->serv->by);
if (cptr->serv->user)
free_user(cptr->serv->user, NULL);
cptr->serv->user = NULL;
}
cptr->serv->up = me.name;
SetConnecting(cptr);
SetOutgoing(cptr);
IRCstats.unknown++;
list_add(&cptr->lclient_node, &unknown_list);
set_sockhost(cptr, aconf->outgoing.hostname);
add_client_to_list(cptr);
if (aconf->outgoing.options & CONNECT_SSL)
{
SetSSLConnectHandshake(cptr);
fd_setselect(cptr->fd, FD_SELECT_WRITE, ircd_SSL_client_handshake, cptr);
}
else
fd_setselect(cptr->fd, FD_SELECT_WRITE, completed_connection, cptr);
return 0;
}
int connect_inet(ConfigItem_link *aconf, aClient *cptr)
{
int len;
struct hostent *hp;
char *bindip;
char buf[BUFSIZE];
int n;
if (!aconf->connect_ip)
return 0; /* handled upstream or shouldn't happen */
if (strchr(aconf->connect_ip, ':'))
SetIPV6(cptr);
cptr->ip = strdup(aconf->connect_ip);
snprintf(buf, sizeof buf, "Outgoing connection: %s", get_client_name(cptr, TRUE));
cptr->fd = fd_socket(IsIPV6(cptr) ? AF_INET6 : AF_INET, SOCK_STREAM, 0, buf);
if (cptr->fd < 0)
{
if (ERRNO == P_EMFILE)
{
sendto_realops("opening stream socket to server %s: No more sockets",
get_client_name(cptr, TRUE));
return 0;
}
report_baderror("opening stream socket to server %s:%s", cptr);
return 0;
}
if (++OpenFiles >= MAXCLIENTS)
{
sendto_realops("No more connections allowed (%s)", cptr->name);
return 0;
}
set_sockhost(cptr, aconf->outgoing.hostname);
if (!aconf->outgoing.bind_ip && iConf.link_bindip)
bindip = iConf.link_bindip;
else
bindip = aconf->outgoing.bind_ip;
if (bindip && strcmp("*", bindip))
{
if (!unreal_bind(cptr->fd, bindip, 0, IsIPV6(cptr)))
{
report_baderror("Error binding to local port for %s:%s -- "
"Your link::outgoing::bind-ip is probably incorrect.", cptr);
return 0;
}
}
set_non_blocking(cptr->fd, cptr);
set_sock_opts(cptr->fd, cptr, IsIPV6(cptr));
return unreal_connect(cptr->fd, cptr->ip, aconf->outgoing.port, IsIPV6(cptr));
}
/** Checks if the system is IPv6 capable.
* IPv6 is always available at compile time (libs, headers), but the OS may
* not have IPv6 enabled (or ipv6 kernel module not loaded). So we better check..
*/
int ipv6_capable(void)
{
int s = socket(AF_INET6, SOCK_STREAM, 0);
if (s < 0)
return 0; /* NO ipv6 */
CLOSE_SOCK(s);
return 1; /* YES */
}