/src/s_bsd.c

/*
 *  ircd-hybrid: an advanced Internet Relay Chat Daemon(ircd).
 *  s_bsd.c: Network functions.
 *
 *  Copyright (C) 2002 by the past and present ircd coders, and others.
 *
 *  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 2 of the License, 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., 59 Temple Place, Suite 330, Boston, MA  02111-1307
 *  USA
 *
 *  $Id: s_bsd.c 465 2006-12-28 02:31:10Z jon $
 */

#include "stdinc.h"
#ifndef _WIN32
#include <netinet/in_systm.h>
#include <netinet/ip.h>
#include <netinet/tcp.h>
#endif
#include "fdlist.h"
#include "s_bsd.h"
#include "client.h"
#include "common.h"
#include "dbuf.h"
#include "event.h"
#include "irc_string.h"
#include "irc_getnameinfo.h"
#include "irc_getaddrinfo.h"
#include "ircd.h"
#include "list.h"
#include "listener.h"
#include "numeric.h"
#include "packet.h"
#include "irc_res.h"
#include "inet_misc.h"
#include "restart.h"
#include "s_auth.h"
#include "s_conf.h"
#include "s_log.h"
#include "s_serv.h"
#include "s_stats.h"
#include "send.h"
#include "memory.h"
#include "s_user.h"
#include "hook.h"

static const char *comm_err_str[] = { "Comm OK", "Error during bind()",
	"Error during DNS lookup", "connect timeout", "Error during connect()",
	"Comm Error"
};

struct Callback *setup_socket_cb = NULL;

static void comm_connect_callback(fde_t * fd, int status);
static PF comm_connect_timeout;
static void comm_connect_dns_callback(void *vptr, struct DNSReply *reply);
static PF comm_connect_tryconnect;

extern void init_netio(void);

/* check_can_use_v6()
 *  Check if the system can open AF_INET6 sockets
 */
void
check_can_use_v6(void)
{
#ifdef IPV6
	int v6;

	if((v6 = socket(AF_INET6, SOCK_STREAM, 0)) < 0)
		ServerInfo.can_use_v6 = 0;
	else
	{
		ServerInfo.can_use_v6 = 1;
#ifdef _WIN32
		closesocket(v6);
#else
		close(v6);
#endif
	}
#else
	ServerInfo.can_use_v6 = 0;
#endif
}

/* get_sockerr - get the error value from the socket or the current errno
 *
 * 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.
 */
int
get_sockerr(int fd)
{
#ifndef _WIN32
	int errtmp = errno;
#else
	int errtmp = WSAGetLastError();
#endif
#ifdef SO_ERROR
	int err = 0;
	socklen_t len = sizeof(err);

	if(-1 < fd && !getsockopt(fd, SOL_SOCKET, SO_ERROR, (char *) &err, (socklen_t *) & len))
	{
		if(err)
			errtmp = err;
	}
	errno = errtmp;
#endif
	return errtmp;
}

/*
 * report_error - report an error from an errno. 
 * Record error to log and also send a copy to all *LOCAL* opers online.
 *
 *        text        is a *format* string for outputing error. It must
 *                contain only two '%s', the first will be replaced
 *                by the sockhost from the client_p, and the latter will
 *                be taken from sys_errlist[errno].
 *
 *        client_p        if not NULL, is the *LOCAL* client associated with
 *                the error.
 *
 * 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...
 * 
 * Actually stderr is still there IFF ircd was run with -s --Rodder
 */

void
report_error(int level, const char *text, const char *who, int error)
{
	who = (who) ? who : "";

	sendto_realops_flags(UMODE_DEBUG, level, text, who, strerror(error));
	log_oper_action(LOG_IOERR_TYPE, NULL, "%s %s %s\n", who, text, strerror(error));
	ilog(L_ERROR, text, who, strerror(error));
}

/*
 * setup_socket()
 *
 * Set the socket non-blocking, and other wonderful bits.
 */
static void *
setup_socket(va_list args)
{
	int fd = va_arg(args, int);
	int opt = 1;

	setsockopt(fd, IPPROTO_TCP, TCP_NODELAY, (char *) &opt, sizeof(opt));

#ifdef IPTOS_LOWDELAY
	opt = IPTOS_LOWDELAY;
	setsockopt(fd, IPPROTO_IP, IP_TOS, (char *) &opt, sizeof(opt));
#endif

#ifndef _WIN32
	fcntl(fd, F_SETFL, fcntl(fd, F_GETFL, 0) | O_NONBLOCK);
#endif

	return NULL;
}

/*
 * init_comm()
 *
 * Initializes comm subsystem.
 */
void
init_comm(void)
{
	setup_socket_cb = register_callback("setup_socket", setup_socket);
	init_netio();
}

/*
 * close_connection
 *        Close the physical connection. This function must make
 *        MyConnect(client_p) == FALSE, and set client_p->from == NULL.
 */
void
close_connection(struct Client *client_p)
{
	struct ConfItem *conf;
	struct AccessItem *aconf;
	struct ClassItem *aclass;

	assert(NULL != client_p);

	if(!IsDead(client_p))
	{
		/* attempt to flush any pending dbufs. Evil, but .. -- adrian */
		/* there is still a chance that we might send data to this socket
		 * even if it is marked as blocked (COMM_SELECT_READ handler is called
		 * before COMM_SELECT_WRITE). Let's try, nothing to lose.. -adx
		 */
		ClearSendqBlocked(client_p);
		send_queued_write(client_p);
	}

	if(IsServer(client_p))
	{
		ServerStats->is_sv++;
		ServerStats->is_sbs += client_p->localClient->send.bytes;
		ServerStats->is_sbr += client_p->localClient->recv.bytes;
		ServerStats->is_sti += CurrentTime - client_p->firsttime;

		/* XXX Does this even make any sense at all anymore?
		 * scheduling a 'quick' reconnect could cause a pile of
		 * nick collides under TSora protocol... -db
		 */
		/*
		 * If the connection has been up for a long amount of time, schedule
		 * a 'quick' reconnect, else reset the next-connect cycle.
		 */
		if((conf = find_conf_exact(SERVER_TYPE,
					   client_p->name, client_p->username, client_p->host)))
		{
			/*
			 * Reschedule a faster reconnect, if this was a automatically
			 * connected configuration entry. (Note that if we have had
			 * a rehash in between, the status has been changed to
			 * CONF_ILLEGAL). But only do this if it was a "good" link.
			 */
			aconf = (struct AccessItem *) map_to_conf(conf);
			aclass = (struct ClassItem *) map_to_conf(aconf->class_ptr);
			aconf->hold = time(NULL);
			aconf->hold += (aconf->hold - client_p->since > HANGONGOODLINK) ?
				HANGONRETRYDELAY : ConFreq(aclass);
			if(nextconnect > aconf->hold)
				nextconnect = aconf->hold;
		}
	}
	else if(IsClient(client_p))
	{
		ServerStats->is_cl++;
		ServerStats->is_cbs += client_p->localClient->send.bytes;
		ServerStats->is_cbr += client_p->localClient->recv.bytes;
		ServerStats->is_cti += CurrentTime - client_p->firsttime;
	}
	else
		ServerStats->is_ni++;

#ifdef HAVE_LIBCRYPTO
	if(client_p->localClient->fd.ssl)
	{
		SSL_set_shutdown(client_p->localClient->fd.ssl, SSL_RECEIVED_SHUTDOWN);

		if(!SSL_shutdown(client_p->localClient->fd.ssl))
			SSL_shutdown(client_p->localClient->fd.ssl);
	}
#endif
	if(client_p->localClient->fd.flags.open)
		fd_close(&client_p->localClient->fd);

	if(HasServlink(client_p))
	{
		if(client_p->localClient->ctrlfd.flags.open)
			fd_close(&client_p->localClient->ctrlfd);
	}

	dbuf_clear(&client_p->localClient->buf_sendq);
	dbuf_clear(&client_p->localClient->buf_recvq);

	MyFree(client_p->localClient->passwd);
	detach_conf(client_p, CONF_TYPE);
	client_p->from = NULL;	/* ...this should catch them! >:) --msa */
}

#ifdef HAVE_LIBCRYPTO
/*
 * ssl_handshake - let OpenSSL initialize the protocol. Register for
 * read/write events if necessary.
 */
static void
ssl_handshake(int fd, struct Client *client_p)
{
	int ret = SSL_accept(client_p->localClient->fd.ssl);
  X509 *cert;

  if ((cert = SSL_get_peer_certificate(client_p->localClient->fd.ssl)) != NULL)
  {
    int res = SSL_get_verify_result(client_p->localClient->fd.ssl);
    if (res == X509_V_OK || res == X509_V_ERR_SELF_SIGNED_CERT_IN_CHAIN ||
        res == X509_V_ERR_UNABLE_TO_VERIFY_LEAF_SIGNATURE ||
        res == X509_V_ERR_DEPTH_ZERO_SELF_SIGNED_CERT)
    {
      /* The client sent a certificate which verified OK */
      memcpy(client_p->certfp, cert->sha1_hash, sizeof(client_p->certfp));
    }
    else
    {
      ilog(L_WARN, "Client %s!%s@%s gave bad SSL client certificate: %d",
          client_p->name, client_p->username, client_p->host, res);
    }
  }

  if (ret <= 0)
    switch (SSL_get_error(client_p->localClient->fd.ssl, ret))
    {
      case SSL_ERROR_WANT_WRITE:
        comm_setselect(&client_p->localClient->fd, COMM_SELECT_WRITE,
	               (PF *) ssl_handshake, client_p, 0);
        return;

      case SSL_ERROR_WANT_READ:
        comm_setselect(&client_p->localClient->fd, COMM_SELECT_READ,
	               (PF *) ssl_handshake, client_p, 0);
        return;

      default:
        exit_client(client_p, client_p, "Error during SSL handshake");
        return;
    }

  execute_callback(auth_cb, client_p);
}
#endif

/*
 * add_connection - creates a client which has just connected to us on 
 * the given fd. The sockhost field is initialized with the ip# of the host.
 * An unique id is calculated now, in case it is needed for auth.
 * The client is sent to the auth module for verification, and not put in
 * any client list yet.
 */
void
add_connection(struct Listener *listener, struct irc_ssaddr *irn, int fd)
{
	struct Client *new_client;

	assert(NULL != listener);

	new_client = make_client(NULL);

	fd_open(&new_client->localClient->fd, fd, 1,
		(listener->flags & LISTENER_SSL) ?
		"Incoming SSL connection" : "Incoming connection");

	/* 
	 * copy address to 'sockhost' as a string, copy it to host too
	 * so we have something valid to put into error messages...
	 */
	memcpy(&new_client->localClient->ip, irn, sizeof(struct irc_ssaddr));

	irc_getnameinfo((struct sockaddr *) &new_client->localClient->ip,
			new_client->localClient->ip.ss_len, new_client->sockhost,
			HOSTIPLEN, NULL, 0, NI_NUMERICHOST);
	new_client->localClient->aftype = new_client->localClient->ip.ss.ss_family;
#ifdef IPV6
	if(new_client->sockhost[0] == ':')
		strlcat(new_client->host, "0", HOSTLEN + 1);

	if(new_client->localClient->aftype == AF_INET6 && ConfigFileEntry.dot_in_ip6_addr == 1)
	{
		strlcat(new_client->host, new_client->sockhost, HOSTLEN + 1);
		strlcat(new_client->host, ".", HOSTLEN + 1);
	}
	else
#endif
		strlcat(new_client->host, new_client->sockhost, HOSTLEN + 1);

	strlcat(new_client->realhost, new_client->host, HOSTLEN + 1);

	new_client->connect_id = ++connect_id;
	new_client->localClient->listener = listener;
	++listener->ref_count;

#ifdef HAVE_LIBCRYPTO
	if(listener->flags & LISTENER_SSL)
	{
		if((new_client->localClient->fd.ssl = SSL_new(ServerInfo.ctx)) == NULL)
		{
			ilog(L_CRIT, "SSL_new() ERROR! -- %s",
			     ERR_error_string(ERR_get_error(), NULL));

			SetDead(new_client);
			exit_client(new_client, new_client, "SSL_new failed");
			return;
		}
		SSL_set_fd(new_client->localClient->fd.ssl, fd);
		ssl_handshake(0, new_client);
	}
	else
#endif
		execute_callback(auth_cb, new_client);
}

/*
 * stolen from squid - its a neat (but overused! :) routine which we
 * can use to see whether we can ignore this errno or not. It is
 * generally useful for non-blocking network IO related errnos.
 *     -- adrian
 */
int
ignoreErrno(int ierrno)
{
	switch (ierrno)
	{
	case EINPROGRESS:
	case EWOULDBLOCK:
#if EAGAIN != EWOULDBLOCK
	case EAGAIN:
#endif
	case EALREADY:
	case EINTR:
#ifdef ERESTART
	case ERESTART:
#endif
		return 1;
	default:
		return 0;
	}
}

/*
 * comm_settimeout() - set the socket timeout
 *
 * Set the timeout for the fd
 */
void
comm_settimeout(fde_t * fd, time_t timeout, PF * callback, void *cbdata)
{
	assert(fd->flags.open);

	fd->timeout = CurrentTime + (timeout / 1000);
	fd->timeout_handler = callback;
	fd->timeout_data = cbdata;
}

/*
 * comm_setflush() - set a flush function
 *
 * A flush function is simply a function called if found during
 * comm_timeouts(). Its basically a second timeout, except in this case
 * I'm too lazy to implement multiple timeout functions! :-)
 * its kinda nice to have it separate, since this is designed for
 * flush functions, and when comm_close() is implemented correctly
 * with close functions, we _actually_ don't call comm_close() here ..
 * -- originally Adrian's notes
 * comm_close() is replaced with fd_close() in fdlist.c 
 */
void
comm_setflush(fde_t * fd, time_t timeout, PF * callback, void *cbdata)
{
	assert(fd->flags.open);

	fd->flush_timeout = CurrentTime + (timeout / 1000);
	fd->flush_handler = callback;
	fd->flush_data = cbdata;
}

/*
 * comm_checktimeouts() - check the socket timeouts
 *
 * All this routine does is call the given callback/cbdata, without closing
 * down the file descriptor. When close handlers have been implemented,
 * this will happen.
 */
void
comm_checktimeouts(void *notused)
{
	int i;
	fde_t *F;
	PF *hdl;
	void *data;

	for(i = 0; i < FD_HASH_SIZE; i++)
		for(F = fd_hash[i]; F != NULL; F = fd_next_in_loop)
		{
			assert(F->flags.open);
			fd_next_in_loop = F->hnext;

			/* check flush functions */
			if(F->flush_handler && F->flush_timeout > 0 &&
			   F->flush_timeout < CurrentTime)
			{
				hdl = F->flush_handler;
				data = F->flush_data;
				comm_setflush(F, 0, NULL, NULL);
				hdl(F, data);
			}

			/* check timeouts */
			if(F->timeout_handler && F->timeout > 0 && F->timeout < CurrentTime)
			{
				/* Call timeout handler */
				hdl = F->timeout_handler;
				data = F->timeout_data;
				comm_settimeout(F, 0, NULL, NULL);
				hdl(F, data);
			}
		}
}

/*
 * void comm_connect_tcp(int fd, const char *host, unsigned short port,
 *                       struct sockaddr *clocal, int socklen,
 *                       CNCB *callback, void *data, int aftype, int timeout)
 * Input: An fd to connect with, a host and port to connect to,
 *        a local sockaddr to connect from + length(or NULL to use the
 *        default), a callback, the data to pass into the callback, the
 *        address family.
 * Output: None.
 * Side-effects: A non-blocking connection to the host is started, and
 *               if necessary, set up for selection. The callback given
 *               may be called now, or it may be called later.
 */
void
comm_connect_tcp(fde_t * fd, const char *host, unsigned short port,
		 struct sockaddr *clocal, int socklen, CNCB * callback,
		 void *data, int aftype, int timeout)
{
	struct addrinfo hints, *res;
	char portname[PORTNAMELEN + 1];

	assert(callback);
	fd->connect.callback = callback;
	fd->connect.data = data;

	fd->connect.hostaddr.ss.ss_family = aftype;
	fd->connect.hostaddr.ss_port = htons(port);

	/* Note that we're using a passed sockaddr here. This is because
	 * generally you'll be bind()ing to a sockaddr grabbed from
	 * getsockname(), so this makes things easier.
	 * XXX If NULL is passed as local, we should later on bind() to the
	 * virtual host IP, for completeness.
	 *   -- adrian
	 */
	if((clocal != NULL) && (bind(fd->fd, clocal, socklen) < 0))
	{
		/* Failure, call the callback with COMM_ERR_BIND */
		comm_connect_callback(fd, COMM_ERR_BIND);
		/* ... and quit */
		return;
	}

	/* Next, if we have been given an IP, get the addr and skip the
	 * DNS check (and head direct to comm_connect_tryconnect().
	 */
	memset(&hints, 0, sizeof(hints));
	hints.ai_family = AF_UNSPEC;
	hints.ai_socktype = SOCK_STREAM;
	hints.ai_flags = AI_PASSIVE | AI_NUMERICHOST;

	snprintf(portname, PORTNAMELEN, "%d", port);

	if(irc_getaddrinfo(host, portname, &hints, &res))
	{
		/* Send the DNS request, for the next level */
		fd->dns_query = MyMalloc(sizeof(struct DNSQuery));
		fd->dns_query->ptr = fd;
		fd->dns_query->callback = comm_connect_dns_callback;
		gethost_byname(host, fd->dns_query);
	}
	else
	{
		/* We have a valid IP, so we just call tryconnect */
		/* Make sure we actually set the timeout here .. */
		assert(res != NULL);
		memcpy(&fd->connect.hostaddr, res->ai_addr, res->ai_addrlen);
		fd->connect.hostaddr.ss_len = res->ai_addrlen;
		fd->connect.hostaddr.ss.ss_family = res->ai_family;
		irc_freeaddrinfo(res);
		comm_settimeout(fd, timeout * 1000, comm_connect_timeout, NULL);
		comm_connect_tryconnect(fd, NULL);
	}
}

/*
 * comm_connect_callback() - call the callback, and continue with life
 */
static void
comm_connect_callback(fde_t * fd, int status)
{
	CNCB *hdl;

	/* This check is gross..but probably necessary */
	if(fd->connect.callback == NULL)
		return;

	/* Clear the connect flag + handler */
	hdl = fd->connect.callback;
	fd->connect.callback = NULL;

	/* Clear the timeout handler */
	comm_settimeout(fd, 0, NULL, NULL);

	/* Call the handler */
	hdl(fd, status, fd->connect.data);
}

/*
 * comm_connect_timeout() - this gets called when the socket connection
 * times out. This *only* can be called once connect() is initially
 * called ..
 */
static void
comm_connect_timeout(fde_t * fd, void *notused)
{
	/* error! */
	comm_connect_callback(fd, COMM_ERR_TIMEOUT);
}

/*
 * comm_connect_dns_callback() - called at the completion of the DNS request
 *
 * The DNS request has completed, so if we've got an error, return it,
 * otherwise we initiate the connect()
 */
static void
comm_connect_dns_callback(void *vptr, struct DNSReply *reply)
{
	fde_t *F = vptr;

	if(reply == NULL)
	{
		MyFree(F->dns_query);
		F->dns_query = NULL;
		comm_connect_callback(F, COMM_ERR_DNS);
		return;
	}

	/* No error, set a 10 second timeout */
	comm_settimeout(F, 30 * 1000, comm_connect_timeout, NULL);

	/* Copy over the DNS reply info so we can use it in the connect() */
	/*
	 * Note we don't fudge the refcount here, because we aren't keeping
	 * the DNS record around, and the DNS cache is gone anyway.. 
	 *     -- adrian
	 */
	memcpy(&F->connect.hostaddr, &reply->addr, reply->addr.ss_len);
	/* The cast is hacky, but safe - port offset is same on v4 and v6 */
	((struct sockaddr_in *) &F->connect.hostaddr)->sin_port = F->connect.hostaddr.ss_port;
	F->connect.hostaddr.ss_len = reply->addr.ss_len;

	/* Now, call the tryconnect() routine to try a connect() */
	MyFree(F->dns_query);
	F->dns_query = NULL;
	comm_connect_tryconnect(F, NULL);
}

/* static void comm_connect_tryconnect(int fd, void *notused)
 * Input: The fd, the handler data(unused).
 * Output: None.
 * Side-effects: Try and connect with pending connect data for the FD. If
 *               we succeed or get a fatal error, call the callback.
 *               Otherwise, it is still blocking or something, so register
 *               to select for a write event on this FD.
 */
static void
comm_connect_tryconnect(fde_t * fd, void *notused)
{
	int retval;

	/* This check is needed or re-entrant s_bsd_* like sigio break it. */
	if(fd->connect.callback == NULL)
		return;

	/* Try the connect() */
	retval = connect(fd->fd, (struct sockaddr *) &fd->connect.hostaddr,
			 fd->connect.hostaddr.ss_len);

	/* Error? */
	if(retval < 0)
	{
#ifdef _WIN32
		errno = WSAGetLastError();
#endif
		/*
		 * If we get EISCONN, then we've already connect()ed the socket,
		 * which is a good thing.
		 *   -- adrian
		 */
		if(errno == EISCONN)
			comm_connect_callback(fd, COMM_OK);
		else if(ignoreErrno(errno))
			/* Ignore error? Reschedule */
			comm_setselect(fd, COMM_SELECT_WRITE, comm_connect_tryconnect, NULL, 0);
		else
			/* Error? Fail with COMM_ERR_CONNECT */
			comm_connect_callback(fd, COMM_ERR_CONNECT);
		return;
	}

	/* If we get here, we've suceeded, so call with COMM_OK */
	comm_connect_callback(fd, COMM_OK);
}

/*
 * comm_errorstr() - return an error string for the given error condition
 */
const char *
comm_errstr(int error)
{
	if(error < 0 || error >= COMM_ERR_MAX)
		return "Invalid error number!";
	return comm_err_str[error];
}

/*
 * comm_open() - open a socket
 *
 * This is a highly highly cut down version of squid's comm_open() which
 * for the most part emulates socket(), *EXCEPT* it fails if we're about
 * to run out of file descriptors.
 */
int
comm_open(fde_t * F, int family, int sock_type, int proto, const char *note)
{
	int fd;

	/* First, make sure we aren't going to run out of file descriptors */
	if(number_fd >= hard_fdlimit)
	{
		errno = ENFILE;
		return -1;
	}

	/*
	 * Next, we try to open the socket. We *should* drop the reserved FD
	 * limit if/when we get an error, but we can deal with that later.
	 * XXX !!! -- adrian
	 */
	fd = socket(family, sock_type, proto);
	if(fd < 0)
	{
#ifdef _WIN32
		errno = WSAGetLastError();
#endif
		return -1;	/* errno will be passed through, yay.. */
	}

	execute_callback(setup_socket_cb, fd);

	/* update things in our fd tracking */
	fd_open(F, fd, 1, note);
	return 0;
}

/*
 * comm_accept() - accept an incoming connection
 *
 * This is a simple wrapper for accept() which enforces FD limits like
 * comm_open() does. Returned fd must be either closed or tagged with
 * fd_open (this function no longer does it).
 */
int
comm_accept(struct Listener *lptr, struct irc_ssaddr *pn)
{
	int newfd;
	socklen_t addrlen = sizeof(struct irc_ssaddr);

	if(number_fd >= hard_fdlimit)
	{
		errno = ENFILE;
		return -1;
	}

	/*
	 * Next, do the accept(). if we get an error, we should drop the
	 * reserved fd limit, but we can deal with that when comm_open()
	 * also does it. XXX -- adrian
	 */
	newfd = accept(lptr->fd.fd, (struct sockaddr *) pn, (socklen_t *) & addrlen);
	if(newfd < 0)
	{
#ifdef _WIN32
		errno = WSAGetLastError();
#endif
		return -1;
	}

#ifdef IPV6
	remove_ipv6_mapping(pn);
#else
	pn->ss_len = addrlen;
#endif

	execute_callback(setup_socket_cb, newfd);

	/* .. and return */
	return newfd;
}

/* 
 * remove_ipv6_mapping() - Removes IPv4-In-IPv6 mapping from an address
 * This function should really inspect the struct itself rather than relying
 * on inet_pton and inet_ntop.  OSes with IPv6 mapping listening on both
 * AF_INET and AF_INET6 map AF_INET connections inside AF_INET6 structures
 * 
 */
#ifdef IPV6
void
remove_ipv6_mapping(struct irc_ssaddr *addr)
{
	if(addr->ss.ss_family == AF_INET6)
	{
		struct sockaddr_in6 *v6;

		v6 = (struct sockaddr_in6 *) addr;
		if(IN6_IS_ADDR_V4MAPPED(&v6->sin6_addr))
		{
			char v4ip[HOSTIPLEN];
			struct sockaddr_in *v4 = (struct sockaddr_in *) addr;
			inetntop(AF_INET6, &v6->sin6_addr, v4ip, HOSTIPLEN);
			inet_pton(AF_INET, v4ip, &v4->sin_addr);
			addr->ss.ss_family = AF_INET;
			addr->ss_len = sizeof(struct sockaddr_in);
		}
		else
			addr->ss_len = sizeof(struct sockaddr_in6);
	}
	else
		addr->ss_len = sizeof(struct sockaddr_in);
}
#endif