Summer of Code 2005: improve libalias - part 1 of 2

With the first part of my previous Summer of Code work, we get:

-made libalias modular:

 -support for 'particular' protocols (like ftp/irc/etcetc) is no more
  hardcoded inside libalias, but it's available through external
  modules loadable at runtime

 -modules are available both in kernel (/boot/kernel/alias_*.ko) and
  user land (/lib/libalias_*)

 -protocols/applications modularized are: cuseeme, ftp, irc, nbt, pptp,
  skinny and smedia

-added logging support for kernel side

-cleanup

After a buildworld, do a 'mergemaster -i' to install the file libalias.conf
in /etc or manually copy it.

During startup (and after every HUP signal) user land applications running
the new libalias will try to read a file in /etc called libalias.conf:
that file contains the list of modules to load.

User land applications affected by this commit are ppp and natd:
if libalias.conf is present in /etc you won't notice any difference.

The only kernel land bit affected by this commit is ng_nat:
if you are using ng_nat, and it doesn't correctly handle
ftp/irc/etcetc sessions anymore, remember to kldload
the correspondent module (i.e. kldload alias_ftp).

General information and details about the inner working are available
in the libalias man page under the section 'MODULAR ARCHITECTURE
(AND ipfw(4) SUPPORT)'.

NOTA BENE: this commit affects _ONLY_ libalias, ipfw in-kernel nat
support will be part of the next libalias-related commit.

Approved by: glebius
Reviewed by: glebius, ru

1 files changed, 153 insertions, 0 deletions

diff --git a/sys/netinet/libalias/alias_dummy.c b/sys/netinet/libalias/alias_dummy.c
new file mode 100644
index 0000000..fc6a0f9
--- /dev/null
+++ b/sys/netinet/libalias/alias_dummy.c
@@ -0,0 +1,153 @@
+/*-
+ * Copyright (c) 2005 Paolo Pisati <piso@FreeBSD.org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <sys/cdefs.h>
+__FBSDID("$FreeBSD$");
+
+/* 
+ * Alias_dummy is just an empty skeleton used to demostrate how to write
+ * a module for libalias, that will run unalterated in userland or in
+ * kernel land.
+ */
+
+#ifdef _KERNEL
+#include <sys/param.h>
+#include <sys/kernel.h>
+#include <sys/module.h>
+#else
+#include <errno.h>
+#include <sys/types.h>
+#include <stdio.h>
+#endif
+
+#include <netinet/in_systm.h>
+#include <netinet/in.h>
+#include <netinet/ip.h>
+#include <netinet/udp.h>
+
+#ifdef _KERNEL
+#include <netinet/libalias/alias_local.h>
+#include <netinet/libalias/alias_mod.h>
+#else
+#include "alias_local.h"
+#include "alias_mod.h"
+#endif
+
+static void
+AliasHandleDummy(struct libalias *la, struct ip *ip, struct alias_data *ah);
+
+static int 
+fingerprint(struct libalias *la, struct ip *pip, struct alias_data *ah)
+{
+
+	/* 
+	 * Check here all the data that will be used later, if any field 
+	 * is empy/NULL, return a -1 value.
+	 */
+	if (ah->dport == NULL || ah->sport == NULL || ah->lnk == NULL || 
+		ah->maxpktsize == 0)
+		return (-1);
+	/* 
+	 * Fingerprint the incoming packet, if it matches any conditions 
+	 * return an OK value.
+	 */
+	if (ntohs(*ah->dport) == 123
+	    || ntohs(*ah->sport) == 456)
+		return (0); /* I know how to handle it. */
+	return (-1); /* I don't recognize this packet. */
+}
+
+/* 
+ * Wrap in this general purpose function, the real function used to alias the 
+ * packets.
+ */
+
+static int 
+protohandler(struct libalias *la, struct ip *pip, struct alias_data *ah)
+{
+	
+	AliasHandleDummy(la, pip, ah);
+	return (0);
+}
+
+/* 
+ * NOTA BENE: the next variable MUST NOT be renamed in any case if you want 
+ * your module to work in userland, cause it's used to find and use all 
+ * the protocol handlers present in every module.
+ * So WATCH OUT, your module needs this variables and it needs it with 
+ * ITS EXACT NAME: handlers.
+ */
+
+struct proto_handler handlers [] = {
+	{ 
+	  .pri = 666, 
+	  .dir = IN|OUT, 
+	  .proto = UDP|TCP, 
+	  .fingerprint = &fingerprint, 
+	  .protohandler = &protohandler
+	}, 
+	{ EOH }
+};
+
+static int
+mod_handler(module_t mod, int type, void *data)
+{
+	int error;
+
+	switch (type) {	  
+	case MOD_LOAD:
+		error = 0;
+		LibAliasAttachHandlers(handlers);
+		break;
+	case MOD_UNLOAD:
+		error = 0;
+		LibAliasDetachHandlers(handlers);
+		break;
+	default:
+		error = EINVAL;
+	}
+	return (error);
+}
+
+#ifdef _KERNEL
+static
+#endif
+moduledata_t alias_mod = {
+       "alias_dummy", mod_handler, NULL
+};
+
+#ifdef	_KERNEL
+DECLARE_MODULE(alias_dummy, alias_mod, SI_SUB_DRIVERS, SI_ORDER_SECOND);
+MODULE_VERSION(alias_dummy, 1);
+MODULE_DEPEND(alias_dummy, libalias, 1, 1, 1);
+#endif
+
+static void
+AliasHandleDummy(struct libalias *la, struct ip *ip, struct alias_data *ah)
+{
+	; /* Dummy. */
+}
+