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, 78 insertions, 4 deletions

diff --git a/sys/netinet/libalias/alias_ftp.c b/sys/netinet/libalias/alias_ftp.c
index d91e1cd..6016f1b 100644
--- a/sys/netinet/libalias/alias_ftp.c
+++ b/sys/netinet/libalias/alias_ftp.c
@@ -72,12 +72,13 @@ __FBSDID("$FreeBSD$");
 #ifdef _KERNEL
 #include <sys/param.h>
 #include <sys/ctype.h>
-#include <sys/libkern.h>
+#include <sys/systm.h>
+#include <sys/kernel.h>
+#include <sys/module.h>
 #else
+#include <errno.h>
 #include <sys/types.h>
-#include <ctype.h>
 #include <stdio.h>
-#include <string.h>
 #endif
 
 #include <netinet/in_systm.h>
@@ -88,8 +89,81 @@ __FBSDID("$FreeBSD$");
 #ifdef _KERNEL
 #include <netinet/libalias/alias.h>
 #include <netinet/libalias/alias_local.h>
+#include <netinet/libalias/alias_mod.h>
 #else
 #include "alias_local.h"
+#include "alias_mod.h"
+#endif
+
+#define FTP_CONTROL_PORT_NUMBER 21
+
+static void
+AliasHandleFtpOut(struct libalias *, struct ip *, struct alias_link *,	
+		  int maxpacketsize);
+
+static int 
+fingerprint(struct libalias *la, struct ip *pip, struct alias_data *ah)
+{
+
+	if (ah->dport == NULL || ah->sport == NULL || ah->lnk == NULL || 
+		ah->maxpktsize == 0)
+		return (-1);
+	if (ntohs(*ah->dport) == FTP_CONTROL_PORT_NUMBER
+	    || ntohs(*ah->sport) == FTP_CONTROL_PORT_NUMBER)
+		return (0);
+	return (-1);
+}
+
+static int 
+protohandler(struct libalias *la, struct ip *pip, struct alias_data *ah)
+{
+	
+	AliasHandleFtpOut(la, pip, ah->lnk, ah->maxpktsize);
+	return (0);
+}
+
+struct proto_handler handlers[] = {
+	{ 
+	  .pri = 80, 
+	  .dir = OUT, 
+	  .proto = 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_ftp", mod_handler, NULL
+};
+
+#ifdef	_KERNEL
+DECLARE_MODULE(alias_ftp, alias_mod, SI_SUB_DRIVERS, SI_ORDER_SECOND);
+MODULE_VERSION(alias_ftp, 1);
+MODULE_DEPEND(alias_ftp, libalias, 1, 1, 1);
 #endif
 
 #define FTP_CONTROL_PORT_NUMBER 21
@@ -112,7 +186,7 @@ static int	ParseFtp227Reply(struct libalias *la, char *, int);
 static int	ParseFtp229Reply(struct libalias *la, char *, int);
 static void	NewFtpMessage(struct libalias *la, struct ip *, struct alias_link *, int, int);
 
-void
+static void
 AliasHandleFtpOut(
     struct libalias *la,
     struct ip *pip,		/* IP packet to examine/patch */