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, 157 insertions, 0 deletions

diff --git a/sys/netinet/libalias/alias_mod.h b/sys/netinet/libalias/alias_mod.h
new file mode 100644
index 0000000..5e193e9
--- /dev/null
+++ b/sys/netinet/libalias/alias_mod.h
@@ -0,0 +1,157 @@
+/*-
+ * 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.
+ *
+ * $FreeBSD$
+ */
+
+/*
+ * Alias_mod.h defines the outside world interfaces for the packet aliasing
+ * modular framework
+ */
+
+#ifndef _ALIAS_MOD_H_
+#define _ALIAS_MOD_H_
+
+#ifdef _KERNEL
+MALLOC_DECLARE(M_ALIAS);
+
+/* Use kernel allocator. */
+#if defined(_SYS_MALLOC_H_)
+#define	malloc(x)	malloc(x, M_ALIAS, M_NOWAIT|M_ZERO)
+#define	calloc(x, n)	malloc(x*n)
+#define	free(x)		free(x, M_ALIAS)
+#endif
+#endif
+
+/* Protocol handlers struct & function. */
+
+/* Packet flow direction. */
+#define IN                              1 
+#define OUT                             2 
+
+/* Working protocol. */
+#define IP                              1
+#define TCP                             2
+#define UDP                             4
+
+/* 
+ * Data passed to protocol handler module, it must be filled
+ * right before calling find_handler() to determine which
+ * module is elegible to be called.
+ */
+
+struct alias_data {	
+	struct alias_link       *lnk;            
+	struct in_addr          *oaddr;         /* Original address. */
+	struct in_addr          *aaddr;         /* Alias address. */ 
+	uint16_t                *aport;         /* Alias port. */
+	uint16_t                *sport, *dport;	/* Source & destination port */
+	uint16_t                maxpktsize;     /* Max packet size. */
+}; 
+
+/* 
+ * This structure contains all the information necessary to make
+ * a protocol handler correctly work.
+ */
+
+struct proto_handler {
+	u_int pri;                                              /* Handler priority. */
+        int16_t dir;                                            /* Flow direction. */
+	uint8_t proto;                                          /* Working protocol. */	
+	int (*fingerprint)(struct libalias *la,                 /* Fingerprint * function. */
+		 struct ip *pip, struct alias_data *ah);
+	int (*protohandler)(struct libalias *la,                /* Aliasing * function. */
+		 struct ip *pip, struct alias_data *ah);                 
+	LIST_ENTRY(proto_handler) entries;
+};
+
+
+/* 
+ * Used only in userland when libalias needs to keep track of all
+ * module loaded. In kernel land (kld mode) we don't need to care
+ * care about libalias modules cause it's kld to do it for us.
+ */
+
+#define DLL_LEN         32
+struct dll {	
+	char            name[DLL_LEN];  /* Name of module. */
+	void            *handle;        /* 
+					 * Ptr to shared obj obtained through
+					 * dlopen() - use this ptr to get access
+					 * to any symbols from a loaded module 					 
+					 * via dlsym(). 
+					 */
+	SLIST_ENTRY(dll)        next;
+};
+
+/* Functions used with protocol handlers. */
+
+void            handler_chain_init(void);
+void            handler_chain_destroy(void);
+int             LibAliasAttachHandlers(struct proto_handler *);
+int             LibAliasDetachHandlers(struct proto_handler *);
+int             detach_handler(struct proto_handler *);
+int             find_handler(int8_t, int8_t, struct libalias *, 
+			   struct ip *, struct alias_data *);
+struct proto_handler *first_handler(void);
+
+/* Functions used with dll module. */
+
+void            dll_chain_init(void);
+void            dll_chain_destroy(void);
+int             attach_dll(struct dll *);
+void            *detach_dll(char *);
+struct dll      *walk_dll_chain(void);
+
+/* End of handlers. */
+#define EOH     -1
+
+/* 
+ * Some defines borrowed from sys/module.h used to compile a kld
+ * in userland as a shared lib.
+ */
+
+#ifndef _KERNEL
+typedef enum modeventtype {
+        MOD_LOAD,
+        MOD_UNLOAD,
+        MOD_SHUTDOWN,
+        MOD_QUIESCE
+} modeventtype_t;
+        
+typedef struct module *module_t;
+typedef int (*modeventhand_t)(module_t, int /* modeventtype_t */, void *);
+
+/*
+ * Struct for registering modules statically via SYSINIT.
+ */
+typedef struct moduledata {
+        const char      *name;          /* module name */
+        modeventhand_t  evhand;         /* event handler */
+        void            *priv;          /* extra data */
+} moduledata_t;
+#endif
+
+#endif				/* !_ALIAS_MOD_H_ */