2 files changed, 136 insertions, 17 deletions

diff --git a/Documentation/filesystems/nfs/nfsroot.txt b/Documentation/filesystems/nfs/nfsroot.txt
index a1030bea60d3..d2963123eb1c 100644
--- a/Documentation/filesystems/nfs/nfsroot.txt
+++ b/Documentation/filesystems/nfs/nfsroot.txt
@@ -5,6 +5,7 @@ Written 1996 by Gero Kuhlmann <gero@gkminix.han.de>
 Updated 1997 by Martin Mares <mj@atrey.karlin.mff.cuni.cz>
 Updated 2006 by Nico Schottelius <nico-kernel-nfsroot@schottelius.org>
 Updated 2006 by Horms <horms@verge.net.au>
+Updated 2018 by Chris Novakovic <chris@chrisn.me.uk>
 
 
 
@@ -79,7 +80,7 @@ nfsroot=[<server-ip>:]<root-dir>[,<nfs-options>]
 
 
 ip=<client-ip>:<server-ip>:<gw-ip>:<netmask>:<hostname>:<device>:<autoconf>:
-   <dns0-ip>:<dns1-ip>
+   <dns0-ip>:<dns1-ip>:<ntp0-ip>
 
   This parameter tells the kernel how to configure IP addresses of devices
   and also how to set up the IP routing table. It was originally called
@@ -178,9 +179,18 @@ ip=<client-ip>:<server-ip>:<gw-ip>:<netmask>:<hostname>:<device>:<autoconf>:
   <dns1-ip>     IP address of secondary nameserver.
                 See <dns0-ip>.
 
-  After configuration (whether manual or automatic) is complete, a file is
-  created at /proc/net/pnp in the following format; lines are omitted if
-  their respective value is empty following configuration.
+  <ntp0-ip>     IP address of a Network Time Protocol (NTP) server.
+                Value is exported to /proc/net/ipconfig/ntp_servers, but is
+                otherwise unused (see below).
+
+                Default: None if not using autoconfiguration; determined
+                automatically if using autoconfiguration.
+
+  After configuration (whether manual or automatic) is complete, two files
+  are created in the following format; lines are omitted if their respective
+  value is empty following configuration:
+
+  - /proc/net/pnp:
 
         #PROTO: <DHCP|BOOTP|RARP|MANUAL>        (depending on configuration method)
         domain <dns-domain>                     (if autoconfigured, the DNS domain)
@@ -189,13 +199,26 @@ ip=<client-ip>:<server-ip>:<gw-ip>:<netmask>:<hostname>:<device>:<autoconf>:
         nameserver <dns2-ip>                    (tertiary name server IP)
         bootserver <server-ip>                  (NFS server IP)
 
-  <dns-domain> and <dns2-ip> are requested during autoconfiguration; they
-  cannot be specified as part of the "ip=" kernel command line parameter.
+  - /proc/net/ipconfig/ntp_servers:
+
+        <ntp0-ip>                               (NTP server IP)
+        <ntp1-ip>                               (NTP server IP)
+        <ntp2-ip>                               (NTP server IP)
+
+  <dns-domain> and <dns2-ip> (in /proc/net/pnp) and <ntp1-ip> and <ntp2-ip>
+  (in /proc/net/ipconfig/ntp_servers) are requested during autoconfiguration;
+  they cannot be specified as part of the "ip=" kernel command line parameter.
 
   Because the "domain" and "nameserver" options are recognised by DNS
   resolvers, /etc/resolv.conf is often linked to /proc/net/pnp on systems
   that use an NFS root filesystem.
 
+  Note that the kernel will not synchronise the system time with any NTP
+  servers it discovers; this is the responsibility of a user space process
+  (e.g. an initrd/initramfs script that passes the IP addresses listed in
+  /proc/net/ipconfig/ntp_servers to an NTP client before mounting the real
+  root filesystem if it is on NFS).
+
 
 nfsrootdebug
 
diff --git a/net/ipv4/ipconfig.c b/net/ipv4/ipconfig.c
index 9abf833f3a99..d839d74853fc 100644
--- a/net/ipv4/ipconfig.c
+++ b/net/ipv4/ipconfig.c
@@ -28,6 +28,9 @@
  *
  *  Multiple Nameservers in /proc/net/pnp
  *              --  Josef Siemes <jsiemes@web.de>, Aug 2002
+ *
+ *  NTP servers in /proc/net/ipconfig/ntp_servers
+ *              --  Chris Novakovic <chris@chrisn.me.uk>, April 2018
  */
 
 #include <linux/types.h>
@@ -93,6 +96,7 @@
 #define CONF_TIMEOUT_MAX        (HZ*30) /* Maximum allowed timeout */
 #define CONF_NAMESERVERS_MAX   3       /* Maximum number of nameservers
                                            - '3' from resolv.h */
+#define CONF_NTP_SERVERS_MAX   3        /* Maximum number of NTP servers */
 
 #define NONE cpu_to_be32(INADDR_NONE)
 #define ANY cpu_to_be32(INADDR_ANY)
@@ -152,6 +156,7 @@ static int ic_proto_used;			/* Protocol used, if any */
 #define ic_proto_used 0
 #endif
 static __be32 ic_nameservers[CONF_NAMESERVERS_MAX]; /* DNS Server IP addresses */
+static __be32 ic_ntp_servers[CONF_NTP_SERVERS_MAX]; /* NTP server IP addresses */
 static u8 ic_domain[64];                /* DNS (not NIS) domain name */
 
 /*
@@ -579,6 +584,15 @@ static inline void __init ic_nameservers_predef(void)
                 ic_nameservers[i] = NONE;
 }
 
+/* Predefine NTP servers */
+static inline void __init ic_ntp_servers_predef(void)
+{
+        int i;
+
+        for (i = 0; i < CONF_NTP_SERVERS_MAX; i++)
+                ic_ntp_servers[i] = NONE;
+}
+
 /*
  *      DHCP/BOOTP support.
  */
@@ -674,6 +688,7 @@ ic_dhcp_init_options(u8 *options, struct ic_device *d)
                         17,     /* Boot path */
                         26,     /* MTU */
                         40,     /* NIS domain name */
+                        42,     /* NTP servers */
                 };
 
                 *e++ = 55;      /* Parameter request list */
@@ -753,12 +768,13 @@ static void __init ic_bootp_init_ext(u8 *e)
  */
 static inline void __init ic_bootp_init(void)
 {
-        /* Re-initialise all name servers to NONE, in case any were set via the
-         * "ip=" or "nfsaddrs=" kernel command line parameters: any IP addresses
-         * specified there will already have been decoded but are no longer
-         * needed
+        /* Re-initialise all name servers and NTP servers to NONE, in case any
+         * were set via the "ip=" or "nfsaddrs=" kernel command line parameters:
+         * any IP addresses specified there will already have been decoded but
+         * are no longer needed
          */
         ic_nameservers_predef();
+        ic_ntp_servers_predef();
 
         dev_add_pack(&bootp_packet_type);
 }
@@ -922,6 +938,15 @@ static void __init ic_do_bootp_ext(u8 *ext)
                 ic_bootp_string(utsname()->domainname, ext+1, *ext,
                                 __NEW_UTS_LEN);
                 break;
+        case 42:        /* NTP servers */
+                servers = *ext / 4;
+                if (servers > CONF_NTP_SERVERS_MAX)
+                        servers = CONF_NTP_SERVERS_MAX;
+                for (i = 0; i < servers; i++) {
+                        if (ic_ntp_servers[i] == NONE)
+                                memcpy(&ic_ntp_servers[i], ext+1+4*i, 4);
+                }
+                break;
         }
 }
 
@@ -1268,6 +1293,7 @@ static int __init ic_dynamic(void)
 
 #ifdef CONFIG_PROC_FS
 
+/* Name servers: */
 static int pnp_seq_show(struct seq_file *seq, void *v)
 {
         int i;
@@ -1306,7 +1332,7 @@ static const struct file_operations pnp_seq_fops = {
 };
 
 /* Create the /proc/net/ipconfig directory */
-static int ipconfig_proc_net_init(void)
+static int __init ipconfig_proc_net_init(void)
 {
         ipconfig_dir = proc_net_mkdir(&init_net, "ipconfig", init_net.proc_net);
         if (!ipconfig_dir)
@@ -1314,6 +1340,52 @@ static int ipconfig_proc_net_init(void)
 
         return 0;
 }
+
+/* Create a new file under /proc/net/ipconfig */
+static int ipconfig_proc_net_create(const char *name,
+                                    const struct file_operations *fops)
+{
+        char *pname;
+        struct proc_dir_entry *p;
+
+        if (!ipconfig_dir)
+                return -ENOMEM;
+
+        pname = kasprintf(GFP_KERNEL, "%s%s", "ipconfig/", name);
+        if (!pname)
+                return -ENOMEM;
+
+        p = proc_create(pname, 0444, init_net.proc_net, fops);
+        kfree(pname);
+        if (!p)
+                return -ENOMEM;
+
+        return 0;
+}
+
+/* Write NTP server IP addresses to /proc/net/ipconfig/ntp_servers */
+static int ntp_servers_seq_show(struct seq_file *seq, void *v)
+{
+        int i;
+
+        for (i = 0; i < CONF_NTP_SERVERS_MAX; i++) {
+                if (ic_ntp_servers[i] != NONE)
+                        seq_printf(seq, "%pI4\n", &ic_ntp_servers[i]);
+        }
+        return 0;
+}
+
+static int ntp_servers_seq_open(struct inode *inode, struct file *file)
+{
+        return single_open(file, ntp_servers_seq_show, NULL);
+}
+
+static const struct file_operations ntp_servers_seq_fops = {
+        .open           = ntp_servers_seq_open,
+        .read           = seq_read,
+        .llseek         = seq_lseek,
+        .release        = single_release,
+};
 #endif /* CONFIG_PROC_FS */
 
 /*
@@ -1388,17 +1460,20 @@ static int __init ip_auto_config(void)
         int err;
         unsigned int i;
 
-        /* Initialise all name servers to NONE (but only if the "ip=" or
-         * "nfsaddrs=" kernel command line parameters weren't decoded, otherwise
-         * we'll overwrite the IP addresses specified there)
+        /* Initialise all name servers and NTP servers to NONE (but only if the
+         * "ip=" or "nfsaddrs=" kernel command line parameters weren't decoded,
+         * otherwise we'll overwrite the IP addresses specified there)
          */
-        if (ic_set_manually == 0)
+        if (ic_set_manually == 0) {
                 ic_nameservers_predef();
+                ic_ntp_servers_predef();
+        }
 
 #ifdef CONFIG_PROC_FS
         proc_create("pnp", 0444, init_net.proc_net, &pnp_seq_fops);
 
-        ipconfig_proc_net_init();
+        if (ipconfig_proc_net_init() == 0)
+                ipconfig_proc_net_create("ntp_servers", &ntp_servers_seq_fops);
 #endif /* CONFIG_PROC_FS */
 
         if (!ic_enable)
@@ -1523,6 +1598,19 @@ static int __init ip_auto_config(void)
                 if (i + 1 == CONF_NAMESERVERS_MAX)
                         pr_cont("\n");
         }
+        /* NTP servers (if any): */
+        for (i = 0; i < CONF_NTP_SERVERS_MAX; i++) {
+                if (ic_ntp_servers[i] != NONE) {
+                        if (i == 0)
+                                pr_info("     ntpserver%u=%pI4",
+                                        i, &ic_ntp_servers[i]);
+                        else
+                                pr_cont(", ntpserver%u=%pI4",
+                                        i, &ic_ntp_servers[i]);
+                }
+                if (i + 1 == CONF_NTP_SERVERS_MAX)
+                        pr_cont("\n");
+        }
 #endif /* !SILENT */
 
         /*
@@ -1620,8 +1708,9 @@ static int __init ip_auto_config_setup(char *addrs)
                 return 1;
         }
 
-        /* Initialise all name servers to NONE */
+        /* Initialise all name servers and NTP servers to NONE */
         ic_nameservers_predef();
+        ic_ntp_servers_predef();
 
         /* Parse string for static IP assignment.  */
         ip = addrs;
@@ -1680,6 +1769,13 @@ static int __init ip_auto_config_setup(char *addrs)
                                                 ic_nameservers[1] = NONE;
                                 }
                                 break;
+                        case 9:
+                                if (CONF_NTP_SERVERS_MAX >= 1) {
+                                        ic_ntp_servers[0] = in_aton(ip);
+                                        if (ic_ntp_servers[0] == ANY)
+                                                ic_ntp_servers[0] = NONE;
+                                }
+                                break;
                         }
                 }
                 ip = cp;