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SubjectRe: DHCP root-path in 2.6
Robert Schwebel <robert@schwebel.de> wrote:
>
> Hi,
>
> the 2.6 behaviour of the root-path option seems to have changed: in 2.4
> it was possible to do this in the DHCP configuration:
>
> option root-path "192.168.1.1:/path/to/root";
>
> to specify an NFS server other than the TFTP boot server where the
> kernel comes from; in 2.6 the code in ipconfig.c which parses this
> option for the IP address has been removed.
>
> Was this done on purpuse or by accident? What's the "correct" way to
> specify the address?

Actually it seems that this functionality was added to 2.4 after 2.5 was
forked off and never got forward ported. I don't know if this was
deliberate or just an oversight.

The original patch seems to apply to 2.5 OK. You get to test it ;)



# This is a BitKeeper generated diff -Nru style patch.
#
# ChangeSet
# 2002/04/01 18:50:30-03:00 martin@meltin.net
# [PATCH] Patch to pull NFS server address off root_server_path
#
# Hi Marcelo,
#
# I've submitted the following patch to Trond Myklebust, who seems to
# think it is OK. Dave Jones has also included it in his 2.5 kernel
# series...
#
# The following patch pulls an NFS server IP address off
# root_server_path (handed out via the DHCP root-path option), if it is
# present. For example, you can do this sort of thing in dhcpd.conf:
#
# root-path = 192.168.1.33:/tftpboot/yip.zImage
#
# This lets you mount your root filesystem off a different machine than
# you booted from, without needing to use kernel command-line
# parameters.
#
# The patch appears to be backwards compatible.
#
# RFC2132 says this about the root-path option:
#
# This option specifies the path-name that contains the client's root
# disk. The path is formatted as a character string consisting of
# characters from the NVT ASCII character set.
#
# This is sufficiently vague to allow the path-name to include an
# IP-address. Also, I found some documentation for FreeBSD saying it
# does this too, so it must be right, because those FreeBSD guys are
# really smart... :-)
#
# The only downside of the patch is that the summary that ipconfig
# prints can be a little odd when the kernel command line overrides
# whatever ipconfig gets from (say) DHCP. The address from the kernel
# command line seems to get stripped off early, so ipconfig reports it,
# but it doesn't report the kernel command line NFS path, since that's
# handled a bit later... This small cosmetic problem looks difficult to
# "fix" without rewriting quite a bit of stuff...
#
# peace & happiness,
# martin
#
# net/ipv4/ipconfig.c
# 2002/03/12 11:42:15-03:00 martin@meltin.net +39 -0
# Patch to pull NFS server address off root_server_path
#
# include/linux/nfs_fs.h
# 2002/03/12 11:25:14-03:00 martin@meltin.net +3 -0
# Patch to pull NFS server address off root_server_path
#
# fs/nfs/nfsroot.c
# 2002/03/12 11:25:14-03:00 martin@meltin.net +1 -32
# Patch to pull NFS server address off root_server_path
#
diff -Nru a/fs/nfs/nfsroot.c b/fs/nfs/nfsroot.c
--- a/fs/nfs/nfsroot.c Wed Jan 28 22:00:06 2004
+++ b/fs/nfs/nfsroot.c Wed Jan 28 22:00:06 2004
@@ -163,37 +163,6 @@


/*
- * Extract IP address from the parameter string if needed. Note that we
- * need to have root_server_addr set _before_ IPConfig gets called as it
- * can override it.
- */
-static void __init root_nfs_parse_addr(char *name)
-{
- int octets = 0;
- char *cp, *cq;
-
- cp = cq = name;
- while (octets < 4) {
- while (*cp >= '0' && *cp <= '9')
- cp++;
- if (cp == cq || cp - cq > 3)
- break;
- if (*cp == '.' || octets == 3)
- octets++;
- if (octets < 4)
- cp++;
- cq = cp;
- }
- if (octets == 4 && (*cp == ':' || *cp == '\0')) {
- if (*cp == ':')
- *cp++ = '\0';
- root_server_addr = in_aton(name);
- strcpy(name, cp);
- }
-}
-
-
-/*
* Parse option string.
*/
static void __init root_nfs_parse(char *name, char *buf)
@@ -344,7 +313,7 @@
line[sizeof(nfs_root_name) - strlen(NFS_ROOT) - 1] = '\0';
sprintf(nfs_root_name, NFS_ROOT, line);
}
- root_nfs_parse_addr(nfs_root_name);
+ root_server_addr = root_nfs_parse_addr(nfs_root_name);
return 1;
}

diff -Nru a/include/linux/nfs_fs.h b/include/linux/nfs_fs.h
--- a/include/linux/nfs_fs.h Wed Jan 28 22:00:06 2004
+++ b/include/linux/nfs_fs.h Wed Jan 28 22:00:06 2004
@@ -276,6 +276,9 @@
extern int nfs_mount(struct sockaddr_in *, char *, struct nfs_fh *);
extern int nfs3_mount(struct sockaddr_in *, char *, struct nfs_fh *);

+/* linux/net/ipv4/ipconfig.c: trims ip addr off front of name, too. */
+extern u32 root_nfs_parse_addr(char *name); /*__init*/
+
/*
* inline functions
*/
diff -Nru a/net/ipv4/ipconfig.c b/net/ipv4/ipconfig.c
--- a/net/ipv4/ipconfig.c Wed Jan 28 22:00:06 2004
+++ b/net/ipv4/ipconfig.c Wed Jan 28 22:00:06 2004
@@ -1105,6 +1105,40 @@
#endif /* CONFIG_PROC_FS */

/*
+ * Extract IP address from the parameter string if needed. Note that we
+ * need to have root_server_addr set _before_ IPConfig gets called as it
+ * can override it.
+ */
+u32 __init root_nfs_parse_addr(char *name)
+{
+ u32 addr;
+ int octets = 0;
+ char *cp, *cq;
+
+ cp = cq = name;
+ while (octets < 4) {
+ while (*cp >= '0' && *cp <= '9')
+ cp++;
+ if (cp == cq || cp - cq > 3)
+ break;
+ if (*cp == '.' || octets == 3)
+ octets++;
+ if (octets < 4)
+ cp++;
+ cq = cp;
+ }
+ if (octets == 4 && (*cp == ':' || *cp == '\0')) {
+ if (*cp == ':')
+ *cp++ = '\0';
+ addr = in_aton(name);
+ strcpy(name, cp);
+ } else
+ addr = INADDR_NONE;
+
+ return addr;
+}
+
+/*
* IP Autoconfig dispatcher.
*/

@@ -1112,6 +1146,7 @@
{
int retries = CONF_OPEN_RETRIES;
unsigned long jiff;
+ u32 addr;

#ifdef CONFIG_PROC_FS
proc_net_create("pnp", 0, pnp_get_info);
@@ -1196,6 +1231,10 @@
/* Device selected manually or only one device -> use it */
ic_dev = ic_first_dev->dev;
}
+
+ addr = root_nfs_parse_addr(root_server_path);
+ if (root_server_addr == INADDR_NONE)
+ root_server_addr = addr;

/*
* Use defaults whereever applicable.
-
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