When acquiring a lease, record the value of the BOOTP siaddr field

contained in the DHCP offer, and write it out to the lease file
as an unquoted value of the "next-server" keyword. The value is ignored
when the lease is read back by dhclient, however other applications
are free to parse it.

The intent behind this change is to allow easier interoperability
with automated installation systems e.g. Cobbler, Foreman, Razor;
FreeBSD installation kernels can automatically probe the network
to discover deployment servers.  There are no plans to MFC this
change unless a backport is specifically requested.

The syntax of the "next-server <ip>" lease keyword is intended to be
identical to that used by the ISC DHCPD server in its configuration files.
The required defines are already present in dhclient but were unused before
this change. (Note: This is NOT the same as Option 66, tftp-server-name).

It has been exercised in a university protocol testbed environment, with
Cobbler and an mfsBSD image containing pc-sysinstall (driven by Cobbler
Cheetah templates). The SYSLINUX memdisk driver is used to boot mfsBSD.
Currently this approach requires that a dedicated system profile has
been created for the node where FreeBSD is to be deployed. If this
is not present, the pc-sysinstall wrapper will be unable to obtain
a node configuration. There is code in progress to allow mfsBSD images
to obtain the required hints from the memdisk environment by parsing
the MBFT ACPI chunk.  This is non-standard as it is not linked into
the platform's ACPI RSDT.

Reviewed by:	des

3 files changed, 13 insertions, 0 deletions

diff --git a/sbin/dhclient/clparse.c b/sbin/dhclient/clparse.c
index 58de8cc..4f234c7 100644
--- a/sbin/dhclient/clparse.c
+++ b/sbin/dhclient/clparse.c
@@ -642,6 +642,10 @@ parse_client_lease_declaration(FILE *cfile, struct client_lease *lease,
 	case FILENAME:
 		lease->filename = parse_string(cfile);
 		return;
+	case NEXT_SERVER:
+		if (!parse_ip_addr(cfile, &lease->nextserver))
+			return;
+		break;
 	case SERVER_NAME:
 		lease->server_name = parse_string(cfile);
 		return;
diff --git a/sbin/dhclient/dhclient.c b/sbin/dhclient/dhclient.c
index f71c8c8..a6ee6db 100644
--- a/sbin/dhclient/dhclient.c
+++ b/sbin/dhclient/dhclient.c
@@ -1063,6 +1063,9 @@ packet_to_lease(struct packet *packet)
 	lease->address.len = sizeof(packet->raw->yiaddr);
 	memcpy(lease->address.iabuf, &packet->raw->yiaddr, lease->address.len);
 
+	lease->nextserver.len = sizeof(packet->raw->siaddr);
+	memcpy(lease->nextserver.iabuf, &packet->raw->siaddr, lease->nextserver.len);
+
 	/* If the server name was filled out, copy it.
 	   Do not attempt to validate the server name as a host name.
 	   RFC 2131 merely states that sname is NUL-terminated (which do
@@ -1874,6 +1877,11 @@ write_client_lease(struct interface_info *ip, struct client_lease *lease,
 		fprintf(leaseFile, "  bootp;\n");
 	fprintf(leaseFile, "  interface \"%s\";\n", ip->name);
 	fprintf(leaseFile, "  fixed-address %s;\n", piaddr(lease->address));
+	if (lease->nextserver.len == sizeof(inaddr_any) &&
+	    0 != memcmp(lease->nextserver.iabuf, &inaddr_any,
+	    sizeof(inaddr_any)))
+		fprintf(leaseFile, "  next-server %s;\n",
+		    piaddr(lease->nextserver));
 	if (lease->filename)
 		fprintf(leaseFile, "  filename \"%s\";\n", lease->filename);
 	if (lease->server_name)
diff --git a/sbin/dhclient/dhcpd.h b/sbin/dhclient/dhcpd.h
index 4762cbd..0644149 100644
--- a/sbin/dhclient/dhcpd.h
+++ b/sbin/dhclient/dhcpd.h
@@ -121,6 +121,7 @@ struct client_lease {
 	struct client_lease	*next;
 	time_t			 expiry, renewal, rebind;
 	struct iaddr		 address;
+	struct iaddr		 nextserver;
 	char			*server_name;
 	char			*filename;
 	struct string_list	*medium;