Re: PF_NETLINK support in glibc

[Andi Kleen <ak@muc.de>]

[cc'ed to Alexey because it is his brain child]

On Thu, Nov 12, 1998 at 07:24:24PM +0100, Philip Blundell wrote:
> >The glibc CVS tree doesn't seem to have support for the new PF_NETLINK  
> >& rtnetlink socket family in Linux 2.1. Unfortunately the linux/* include
> >file conflicts partly with glibc.
> 
> Here's a patch I cooked up to add support for netlink sockets.  Can you (and
> anybody else who's interested) take a look and let me know if it seems OK.

To make it useful at least support for rtnetlink (linux/rtnetlink.h) is needed.
rtnetlink is the IPv4 routing table interface which is the main 
use of netlink currently. 

>   
> I don't have any applications here that use AF_NETLINK so I haven't tested 
> it myself.

Applications using the new netlink interface are:
- gated with ANK's patches from ftp.inr.ac.ru:/ip-routing
- iproute2 (needs a few changes to compile with glibc), available from inr
too. 
- zebra from ftp.zebra.org
- mtr somewhere on www.merit.edu

The beginning of some netlink documentation (not finished) is included
with my snapshot of the rewriten linux networking manpages at
ftp.muc.de:/people/ak/netman*

There is also a problem with NLMSG_NEXT IMHO: it doesn't return NULL at 
the end or when the message is invalid like the similar cmsg function.
The caller has to do the NLMSG_DONE check himself and call NLMSG_OK
before looking at the message. I think it would be better if NLMSG_NEXT
did all so that when it returns != NULL the pointer is guranteed to 
be valid. Unfortunately that would be an API change for existing 
netlink programs.

Also the length argument of NLMSG_NEXT must be a lvalue,
that probably be documented.

-Andi

> 
> p.
> 
> 1998-11-12  Philip Blundell  <philb@gnu.org>
> 
> 	* sysdeps/unix/sysv/linux/netlink/netlink.h: New file, support for 
> 	Linux AF_NETLINK sockets (needed since the kernel version is
> 	unusable).
> 	* sysdeps/unix/sysv/linux/Makefile: Install it.
> 	* sysdeps/unix/sysv/linux/Dist: Distribute it.
> 
> --- libc/sysdeps/unix/sysv/linux/Makefile~	Thu Oct 29 03:07:00 1998
> +++ libc/sysdeps/unix/sysv/linux/Makefile	Thu Nov 12 19:18:52 1998
> @@ -84,7 +84,7 @@
>  		  netinet/if_fddi.h netinet/if_tr.h netinet/igmp.h \
>  		  netipx/ipx.h netash/ash.h netax25/ax25.h netatalk/at.h \
>  		  netrom/netrom.h netpacket/packet.h netrose/rose.h \
> -		  neteconet/ec.h
> +		  neteconet/ec.h netlink/netlink.h
>  endif
>  
>  # Don't compile the ctype glue code, since there is no old non-GNU C library.
> --- libc/sysdeps/unix/sysv/linux/Dist~	Thu Oct 29 03:07:00 1998
> +++ libc/sysdeps/unix/sysv/linux/Dist	Thu Nov 12 19:18:47 1998
> @@ -35,6 +35,7 @@
>  netinet/igmp.h
>  netinet/in_systm.h
>  netinet/ip_fw.h
> +netlink/netlink.h
>  netpacket/packet.h
>  netipx/ipx.h
>  netrom/netrom.h
> --- /dev/null	Sun Oct 12 19:38:15 1997
> +++ libc/sysdeps/unix/sysv/linux/netlink/netlink.h	Thu Nov 12 19:17:20 1998
> @@ -0,0 +1,125 @@
> +/* Definitions for use with Linux AF_NETLINK sockets.
> +   Copyright (C) 1998 Free Software Foundation, Inc.
> +   This file is part of the GNU C Library.
> +
> +   The GNU C Library is free software; you can redistribute it and/or
> +   modify it under the terms of the GNU Library General Public License as
> +   published by the Free Software Foundation; either version 2 of the
> +   License, or (at your option) any later version.
> +
> +   The GNU C Library 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
> +   Library General Public License for more details.
> +
> +   You should have received a copy of the GNU Library General Public
> +   License along with the GNU C Library; see the file COPYING.LIB.  If not,
> +   write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
> +   Boston, MA 02111-1307, USA.  */
> +
> +#ifndef __NETLINK_NETLINK_H
> +#define __NETLINK_NETLINK_H	1
> +
> +#include <features.h>
> +
> +#include <sys/types.h>
> +#include <bits/sockaddr.h>
> +
> +__BEGIN_DECLS
> +
> +struct sockaddr_nl
> +  {
> +    __SOCKADDR_COMMON (nl_);
> +    unsigned short nl_pad;		/* zero.  */
> +    uint32_t nl_pid;			/* process pid.  */
> +    uint32_t nl_groups;			/* multicast groups mask.  */
> +  };
> +
> +#define NETLINK_ROUTE		0	/* Routing/device hook.  */
> +#define NETLINK_SKIP		1	/* Reserved for ENskip.  */
> +#define NETLINK_USERSOCK	2	/* Reserved for user mode 
> +					   socket protocolss.  */
> +#define NETLINK_FIREWALL	3	/* Firewalling hook.  */
> +#define NETLINK_ARPD		8
> +#define NETLINK_ROUTE6		11	/* AF_INET6 route comm channel */
> +#define NETLINK_IP6_FW		13
> +#define NETLINK_TAPBASE		16	/* 16 to 31 are ethertap */
> +
> +#define MAX_LINKS 32		
> +
> +struct nlmsghdr
> +  {
> +    uint32_t nlmsg_len;		/* Length of message including header */
> +    uint16_t nlmsg_type;	/* Message content */
> +    uint16_t nlmsg_flags;	/* Additional flags */
> +    uint32_t nlmsg_seq;		/* Sequence number */
> +    uint32_t nlmsg_pid;		/* Sending process PID */
> +  };
> +
> +/* Flag bits */
> +#define NLM_F_REQUEST	1	/* Message is a request.  */
> +#define NLM_F_MULTI	2	/* Multipart message, terminated by 
> +				   NLMSG_DONE.  */
> +#define NLM_F_ACK	4	/* If operation succeeds, reply with ack.  */
> +#define NLM_F_ECHO	8	/* Echo this request.  */
> +
> +/* Modifiers to GET request */
> +#define NLM_F_ROOT	0x100	/* specify tree	root.  */
> +#define NLM_F_MATCH	0x200	/* return all matching.  */
> +#define NLM_F_ATOMIC	0x400	/* atomic GET.  */
> +#define NLM_F_DUMP	(NLM_F_ROOT|NLM_F_MATCH)
> +
> +/* Modifiers to NEW request */
> +#define NLM_F_REPLACE	0x100	/* Override existing.  */
> +#define NLM_F_EXCL	0x200	/* Do not touch, if it exists.  */
> +#define NLM_F_CREATE	0x400	/* Create, if it does not exist.  */
> +#define NLM_F_APPEND	0x800	/* Add to end of list.  */
> +
> +/*
> +   4.4BSD ADD		NLM_F_CREATE|NLM_F_EXCL
> +   4.4BSD CHANGE	NLM_F_REPLACE
> +
> +   True CHANGE		NLM_F_CREATE|NLM_F_REPLACE
> +   Append		NLM_F_CREATE
> +   Check		NLM_F_EXCL
> + */
> +
> +#define NLMSG_ALIGNTO	4
> +
> +#define NLMSG_ALIGN(len)		\
> +	(((len)+NLMSG_ALIGNTO-1) & ~(NLMSG_ALIGNTO-1) )
> +
> +#define NLMSG_LENGTH(len)		\
> +	((len)+NLMSG_ALIGN(sizeof(struct nlmsghdr)))
> +
> +#define NLMSG_SPACE(len)		\
> +	NLMSG_ALIGN(NLMSG_LENGTH(len))
> +
> +#define NLMSG_DATA(nlh)			\
> +	((void*)(((char*)nlh) + NLMSG_LENGTH(0)))
> +
> +#define NLMSG_NEXT(nlh,len)		\
> +	 ((len) -= NLMSG_ALIGN((nlh)->nlmsg_len), \
> +	  (struct nlmsghdr*)(((char*)(nlh)) + NLMSG_ALIGN((nlh)->nlmsg_len)))
> +
> +#define NLMSG_OK(nlh,len)		\
> +	((len) > 0 && (nlh)->nlmsg_len >= sizeof(struct nlmsghdr) 
> +		&& (nlh)->nlmsg_len <= (len))
> +
> +#define NLMSG_PAYLOAD(nlh,len)		\
> +	((nlh)->nlmsg_len - NLMSG_SPACE((len)))
> +
> +#define NLMSG_NOOP		0x1	/* Nothing.  */
> +#define NLMSG_ERROR		0x2	/* Error.  */
> +#define NLMSG_DONE		0x3	/* End of a dump.  */
> +#define NLMSG_OVERRUN		0x4	/* Data lost.  */
> +
> +struct nlmsgerr
> +  {
> +    int	error;
> +    struct nlmsghdr msg;
> +  };
> +
> +#define NET_MAJOR 36		/* Major 36 is reserved for networking 						*/
> +
> +#endif
> 
>