nfsroot.c

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/*
 *  Copyright (C) 1995, 1996  Gero Kuhlmann <[email protected]>
 *
 *  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 NFS_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\n",
            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\n", 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\n");
    goto out;
out_optionstoolong:
    printk(KERN_ERR "Root-NFS: mount options string too long\n");
    goto out;
out_devnametoolong:
    printk(KERN_ERR "Root-NFS: root device name too long.\n");
    goto out;
}

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\n");
        return -1;
    }

    if (root_nfs_data(nfs_root_parms) < 0)
        return -1;

    *root_device = nfs_root_device;
    *root_data = nfs_root_options;
    return 0;
}