/*

   *  Copyright (C) 1995, 1996  Gero Kuhlmann <gero@gkminix.han.de>
   *
   *  Allow an NFS filesystem to be mounted as root. The way this works is:
   *     (1) Use the IP autoconfig mechanism to set local IP addresses and routes.

   *     (2) Construct the device string and the options string using DHCP
   *         option 17 and/or kernel command line options.
   *     (3) When mount_root() sets up the root file system, pass these strings
   *         to the NFS client's regular mount interface via sys_mount().

   *
   *
   *	Changes:
   *
   *	Alan Cox	:	Removed get_address name clash with FPU.
   *	Alan Cox	:	Reformatted a bit.
   *	Gero Kuhlmann	:	Code cleanup
   *	Michael Rausch  :	Fixed recognition of an incoming RARP answer.
   *	Martin Mares	: (2.0)	Auto-configuration via BOOTP supported.
   *	Martin Mares	:	Manual selection of interface & BOOTP/RARP.
   *	Martin Mares	:	Using network routes instead of host routes,
   *				allowing the default configuration to be used
   *				for normal operation of the host.
   *	Martin Mares	:	Randomized timer with exponential backoff
   *				installed to minimize network congestion.
   *	Martin Mares	:	Code cleanup.
   *	Martin Mares	: (2.1)	BOOTP and RARP made configuration options.
   *	Martin Mares	:	Server hostname generation fixed.
   *	Gerd Knorr	:	Fixed wired inode handling
   *	Martin Mares	: (2.2)	"0.0.0.0" addresses from command line ignored.
   *	Martin Mares	:	RARP replies not tested for server address.
   *	Gero Kuhlmann	: (2.3) Some bug fixes and code cleanup again (please
   *				send me your new patches _before_ bothering
   *				Linus so that I don' always have to cleanup
   *				_afterwards_ - thanks)
   *	Gero Kuhlmann	:	Last changes of Martin Mares undone.
   *	Gero Kuhlmann	: 	RARP replies are tested for specified server
   *				again. However, it's now possible to have
   *				different RARP and NFS servers.
   *	Gero Kuhlmann	:	"0.0.0.0" addresses from command line are
   *				now mapped to INADDR_NONE.
   *	Gero Kuhlmann	:	Fixed a bug which prevented BOOTP path name
   *				from being used (thanks to Leo Spiekman)
   *	Andy Walker	:	Allow to specify the NFS server in nfs_root
   *				without giving a path name

   *	Swen Thümmler	:	Allow to specify the NFS options in nfs_root

   *				without giving a path name. Fix BOOTP request
   *				for domainname (domainname is NIS domain, not
   *				DNS domain!). Skip dummy devices for BOOTP.
   *	Jacek Zapala	:	Fixed a bug which prevented server-ip address
   *				from nfsroot parameter from being used.
   *	Olaf Kirch	:	Adapted to new NFS code.
   *	Jakub Jelinek	:	Free used code segment.
   *	Marko Kohtala	:	Fixed some bugs.
   *	Martin Mares	:	Debug message cleanup
   *	Martin Mares	:	Changed to use the new generic IP layer autoconfig
   *				code. BOOTP and RARP moved there.
   *	Martin Mares	:	Default path now contains host name instead of
   *				host IP address (but host name defaults to IP
   *				address anyway).
   *	Martin Mares	:	Use root_server_addr appropriately during setup.
   *	Martin Mares	:	Rewrote parameter parsing, now hopefully giving
   *				correct overriding.
   *	Trond Myklebust :	Add in preliminary support for NFSv3 and TCP.
   *				Fix bug in root_nfs_addr(). nfs_data.namlen
   *				is NOT for the length of the hostname.
   *	Hua Qin		:	Support for mounting root file system via
   *				NFS over TCP.
   *	Fabian Frederick:	Option parser rebuilt (using parser lib)

   *	Chuck Lever	:	Use super.c's text-based mount option parsing

   *	Chuck Lever	:	Add "nfsrootdebug".

   */

  #include <linux/types.h>
  #include <linux/string.h>

  #include <linux/init.h>

  #include <linux/nfs.h>
  #include <linux/nfs_fs.h>

  #include <linux/utsname.h>

  #include <linux/root_dev.h>
  #include <net/ipconfig.h>

  #include "internal.h"

  #define NFSDBG_FACILITY NFSDBG_ROOT
  
  /* Default path we try to mount. "%s" gets replaced by our IP address */
  #define NFS_ROOT		"/tftpboot/%s"

  /* Default NFSROOT mount options. */

  #define NFS_DEF_OPTIONS		"vers=2,udp,rsize=4096,wsize=4096"

  /* Parameters passed from the kernel command line */

  static char nfs_root_parms[256] __initdata = "";

  /* Text-based mount options passed to super.c */

  static char nfs_root_options[256] __initdata = NFS_DEF_OPTIONS;

  /* Address of NFS server */

  static __be32 servaddr __initdata = htonl(INADDR_NONE);

  
  /* Name of directory to mount */

  static char nfs_export_path[NFS_MAXPATHLEN + 1] __initdata = "";
  
  /* server:export path string passed to super.c */
  static char nfs_root_device[NFS_MAXPATHLEN + 1] __initdata = "";

  #ifdef RPC_DEBUG

  /*

   * When the "nfsrootdebug" kernel command line option is specified,
   * enable debugging messages for NFSROOT.
   */
  static int __init nfs_root_debug(char *__unused)
  {
  	nfs_debug |= NFSDBG_ROOT | NFSDBG_MOUNT;
  	return 1;
  }
  
  __setup("nfsrootdebug", nfs_root_debug);

  #endif

  
  /*

   *  Parse NFS server and directory information passed on the kernel
   *  command line.

   *
   *  nfsroot=[<server-ip>:]<root-dir>[,<nfs-options>]
   *
   *  If there is a "%s" token in the <root-dir> string, it is replaced
   *  by the ASCII-representation of the client's IP address.

   */
  static int __init nfs_root_setup(char *line)
  {
  	ROOT_DEV = Root_NFS;

  	if (line[0] == '/' || line[0] == ',' || (line[0] >= '0' && line[0] <= '9')) {

  		strlcpy(nfs_root_parms, line, sizeof(nfs_root_parms));

  	} else {

  		size_t n = strlen(line) + sizeof(NFS_ROOT) - 1;
  		if (n >= sizeof(nfs_root_parms))
  			line[sizeof(nfs_root_parms) - sizeof(NFS_ROOT) - 2] = '\0';
  		sprintf(nfs_root_parms, NFS_ROOT, line);

  	}

  
  	/*
  	 * Extract the IP address of the NFS server containing our
  	 * root file system, if one was specified.
  	 *
  	 * Note: root_nfs_parse_addr() removes the server-ip from
  	 *	 nfs_root_parms, if it exists.
  	 */
  	root_server_addr = root_nfs_parse_addr(nfs_root_parms);

  	return 1;
  }
  
  __setup("nfsroot=", nfs_root_setup);

  static int __init root_nfs_copy(char *dest, const char *src,
  				     const size_t destlen)
  {
  	if (strlcpy(dest, src, destlen) > destlen)
  		return -1;
  	return 0;
  }
  
  static int __init root_nfs_cat(char *dest, const char *src,

  			       const size_t destlen)

  {

  	size_t len = strlen(dest);
  
  	if (len && dest[len - 1] != ',')
  		if (strlcat(dest, ",", destlen) > destlen)
  			return -1;

  	if (strlcat(dest, src, destlen) > destlen)
  		return -1;
  	return 0;
  }
  
  /*
   * Parse out root export path and mount options from
   * passed-in string @incoming.
   *
   * Copy the export path into @exppath.
   */
  static int __init root_nfs_parse_options(char *incoming, char *exppath,
  					 const size_t exppathlen)
  {
  	char *p;
  
  	/*
  	 * Set the NFS remote path
  	 */
  	p = strsep(&incoming, ",");
  	if (*p != '\0' && strcmp(p, "default") != 0)
  		if (root_nfs_copy(exppath, p, exppathlen))
  			return -1;
  
  	/*
  	 * @incoming now points to the rest of the string; if it
  	 * contains something, append it to our root options buffer
  	 */
  	if (incoming != NULL && *incoming != '\0')
  		if (root_nfs_cat(nfs_root_options, incoming,
  						sizeof(nfs_root_options)))
  			return -1;

  	return 0;
  }
  
  /*
   *  Decode the export directory path name and NFS options from
   *  the kernel command line.  This has to be done late in order to
   *  use a dynamically acquired client IP address for the remote
   *  root directory path.
   *
   *  Returns zero if successful; otherwise -1 is returned.
   */
  static int __init root_nfs_data(char *cmdline)
  {

  	char mand_options[sizeof("nolock,addr=") + INET_ADDRSTRLEN + 1];

  	int len, retval = -1;
  	char *tmp = NULL;
  	const size_t tmplen = sizeof(nfs_export_path);
  
  	tmp = kzalloc(tmplen, GFP_KERNEL);
  	if (tmp == NULL)
  		goto out_nomem;
  	strcpy(tmp, NFS_ROOT);
  
  	if (root_server_path[0] != '\0') {
  		dprintk("Root-NFS: DHCPv4 option 17: %s
  ",
  			root_server_path);
  		if (root_nfs_parse_options(root_server_path, tmp, tmplen))
  			goto out_optionstoolong;
  	}
  
  	if (cmdline[0] != '\0') {
  		dprintk("Root-NFS: nfsroot=%s
  ", cmdline);
  		if (root_nfs_parse_options(cmdline, tmp, tmplen))
  			goto out_optionstoolong;
  	}
  
  	/*
  	 * Append mandatory options for nfsroot so they override
  	 * what has come before
  	 */

  	snprintf(mand_options, sizeof(mand_options), "nolock,addr=%pI4",

  			&servaddr);

  	if (root_nfs_cat(nfs_root_options, mand_options,

  						sizeof(nfs_root_options)))
  		goto out_optionstoolong;
  
  	/*
  	 * Set up nfs_root_device.  For NFS mounts, this looks like
  	 *
  	 *	server:/path
  	 *
  	 * At this point, utsname()->nodename contains our local
  	 * IP address or hostname, set by ipconfig.  If "%s" exists
  	 * in tmp, substitute the nodename, then shovel the whole
  	 * mess into nfs_root_device.
  	 */
  	len = snprintf(nfs_export_path, sizeof(nfs_export_path),
  				tmp, utsname()->nodename);
  	if (len > (int)sizeof(nfs_export_path))
  		goto out_devnametoolong;
  	len = snprintf(nfs_root_device, sizeof(nfs_root_device),
  				"%pI4:%s", &servaddr, nfs_export_path);
  	if (len > (int)sizeof(nfs_root_device))
  		goto out_devnametoolong;
  
  	retval = 0;
  
  out:
  	kfree(tmp);
  	return retval;
  out_nomem:
  	printk(KERN_ERR "Root-NFS: could not allocate memory
  ");
  	goto out;
  out_optionstoolong:
  	printk(KERN_ERR "Root-NFS: mount options string too long
  ");
  	goto out;
  out_devnametoolong:
  	printk(KERN_ERR "Root-NFS: root device name too long.
  ");
  	goto out;
  }
  
  /**
   * nfs_root_data - Return prepared 'data' for NFSROOT mount
   * @root_device: OUT: address of string containing NFSROOT device
   * @root_data: OUT: address of string containing NFSROOT mount options
   *
   * Returns zero and sets @root_device and @root_data if successful,
   * otherwise -1 is returned.
   */
  int __init nfs_root_data(char **root_device, char **root_data)
  {

  	servaddr = root_server_addr;
  	if (servaddr == htonl(INADDR_NONE)) {
  		printk(KERN_ERR "Root-NFS: no NFS server address
  ");
  		return -1;
  	}
  
  	if (root_nfs_data(nfs_root_parms) < 0)
  		return -1;
  
  	*root_device = nfs_root_device;
  	*root_data = nfs_root_options;
  	return 0;
  }