[PATCH] pypxeboot bootloader

[PATCH] pypxeboot bootloader

[Stephen Childs]

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As promised on Friday here is the patch for the pypxeboot bootloader. It 
would be great if someone could try it out and give me some feedback.

Stephen
-- 
Dr. Stephen Childs,
Research Fellow, EGEE Project,    phone:                    +353-1-8961797
Computer Architecture Group,      email:        Stephen.Childs @ cs.tcd.ie
Trinity College Dublin, Ireland   web: http://www.cs.tcd.ie/Stephen.Childs

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# HG changeset patch
# User childss@tg23.testgrid
# Date 1170673641 0
# Node ID 7f1a38c5c08659ae123e5f94696cbca19e4e10fb
# Parent  01ec7dba9ff805a5c74a0318997b747d3e3e3327
Added pypxeboot bootloader for simulating PXE boot for DomUs.
Signed-off-by: Stephen Childs <childss@cs.tcd.ie>

diff -r 01ec7dba9ff8 -r 7f1a38c5c086 tools/pypxeboot/README
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/tools/pypxeboot/README	Mon Feb 05 11:07:21 2007 +0000
@@ -0,0 +1,44 @@
+pypxeboot is a bootloader for xen that simulates PXE behaviour. It runs on 
+Domain 0 as part of the domain creation process and downloads boot information
+from a previously-configured PXELinux server using TFTP.
+
+pypxeboot requires the following external programs:
+
+1) A patched version of udhcp 0.9.8 (http://udhcp.busybox.net/) that supports 
+a user-specified MAC address. The patch is udhcp_usermac.patch, available
+in this distribution. There is also a script needed to output information
+received from the DHCP server. This is called outputpy.udhcp.sh and
+should be installed at /usr/share/udhcpc/
+
+2) The tftp client program (http://www.kernel.org/pub/software/network/tftp/). 
+RPMs are also available from the DAG repository at
+(http://dag.wieers.com/rpm/packages/tftp/)
+
+To use pypxeboot, add the following lines to your Xen domain configuration
+file:
+
+bootloader="/usr/bin/pypxeboot"
+bootargs=vif[0]
+
+If the pxelinux.cfg entry is set to localboot you should see output like this:
+
+[root@tg23 pypxeboot]# xm create  cagnode50-slc308
+Using config file "/etc/xen/cagnode50-slc308".
+pypxeboot: requesting info for MAC address AA:00:86:e2:35:72
+pypxeboot: getting cfg for IP 134.226.53.114 (86E23572) from server 192.168.12.1
+pypxeboot: dropping to pygrub for local boot
+Going to boot Scientific Linux CERN Xen DomU-xenU (2.4.21-47.0.1.EL.cernxenU)
+  kernel: /vmlinuz-2.4.21-47.0.1.EL.cernxenU
+  initrd: /initrd-2.4.21-47.0.1.EL.cernxenU.img
+
+and something like this if the pxelinux.cfg entry specifies a network boot:
+
+[root@tg23 pypxeboot]# xm create  cagnode50-slc308
+Using config file "/etc/xen/cagnode50-slc308".
+pypxeboot: requesting info for MAC address AA:00:86:e2:35:72
+pypxeboot: getting cfg for IP 134.226.53.114 (86E23572) from server 192.168.12.1
+pypxeboot: downloading initrd using cmd: tftp -c get 192.168.12.1:slc308_i386_xen/initrd.img
+pypxeboot: downloading kernel using cmd: tftp -c get 192.168.12.1:slc308_i386_xen/vmlinuz
+Started domain cagnode50
+
+The kernel and initrd on the tftp server need to be XenLinux images.
diff -r 01ec7dba9ff8 -r 7f1a38c5c086 tools/pypxeboot/outputpy.udhcp.sh
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/tools/pypxeboot/outputpy.udhcp.sh	Mon Feb 05 11:07:21 2007 +0000
@@ -0,0 +1,42 @@
+#!/bin/sh
+#
+# outputpy.udhcp.sh: a simple script called by udhcpc when a lease is
+# obtained. The script takes information passed by udhcpc as environment
+# variables and outputs it formatted as a python dict. Only the variables
+# needed by pypxeboot are currently printed: others are listed in comments
+# for reference.
+# Copyright 2007 Trinity College Dublin
+# Author: Stephen Childs <childss@cs.tcd.ie>
+
+# we only need to process "bound" events
+if [ "$1" == "bound" ]; then
+echo "{ 'ip' : '$ip', 'siaddr' : '$siaddr', 'sname' : '$sname', \
+'boot_file' : '$boot_file', \
+'subnet' : '$subnet', \
+'timezone' : '$timezone', \
+'router' : '$router', \
+'bootfile' : '$bootfile'}" #        - The bootfile name
+fi
+exit 0
+
+#        timesvr         - A list of time servers
+#        namesvr 
+#        dns  
+#        logsvr          - A list of MIT-LCS UDP log servers
+#        cookiesvr       - A list of RFC 865 cookie servers
+#        lprsvr          - A list of LPR servers
+#        hostname        - The assigned hostname
+#        bootsize        - The length in 512 octect blocks of the bootfile
+#        domain          - The domain name of the network
+#        swapsvr         - The IP address of the client's swap server
+#        rootpath        - The path name of the client's root disk
+#        ipttl           - The TTL to use for this network
+#        mtu             - The MTU to use for this network
+#        broadcast       - The broadcast address for this network
+#        ntpsrv          - A list of NTP servers
+#        wins            - A list of WINS servers
+#        lease           - The lease time, in seconds
+#        dhcptype        - DHCP message type (safely ignored)
+#        serverid        - The IP of the server
+#        message         - Reason for a DHCPNAK
+#        tftp            - The TFTP server name
diff -r 01ec7dba9ff8 -r 7f1a38c5c086 tools/pypxeboot/pypxeboot
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/tools/pypxeboot/pypxeboot	Mon Feb 05 11:07:21 2007 +0000
@@ -0,0 +1,202 @@
+#!/usr/bin/python
+#
+# pypxeboot - simple python-based bootloader to fake PXE booting for Xen DomUs
+# Uses a modified version of udhcpc that allows MAC address to be passed on
+# the command line. Also uses tftp client to download configuration and images
+#
+# Copyright 2007 Trinity College Dublin
+# Stephen Childs <childss@cs.tcd.ie>
+#
+# This software may be freely redistributed under the terms of the GNU
+# general public license.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, write to the Free Software
+# Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+#
+
+import commands,sys,re,os,getopt
+
+udhcpc_command="/usr/bin/udhcpc"
+udhcpc_script="/usr/share/udhcpc/outputpy.udhcp.sh"
+havekernelargs=False
+
+def run_pygrub():
+    arglist=[]
+    for arg in sys.argv[1:]:
+        if not (macre.match(arg)):
+            arglist.append(arg)
+
+    program="/usr/bin/pygrub"
+
+    os.execvp(program, (program,) +  tuple(arglist))
+
+def tftp_success(statusoutput):
+    errorre=re.compile("Error*")
+    if errorre.match(statusoutput[1]):
+        return False
+    else:
+        return True
+
+# get arguments from calling program -- most important is MAC address
+macre=re.compile("mac*=*",re.IGNORECASE)
+outputre=re.compile("--output*",re.IGNORECASE)
+
+def usage():
+    print >> sys.stderr, "Usage: %s [-q|--quiet] [--output=] [--entry=] <image>" %(sys.argv[0],)
+
+try:
+    opts, args = getopt.gnu_getopt(sys.argv[1:], 'qh::',
+                                   ["quiet", "help", "output=", "entry=", "mac=",
+                                    "isconfig"])
+except getopt.GetoptError:
+    usage()
+    sys.exit(1)
+
+if len(args) < 1:
+    usage()
+    sys.exit(1)
+
+output = None
+
+for o, a in opts:
+    if o in  ("--output",):
+        output = a
+
+if output is None or output == "-":
+    outputfd = sys.stdout.fileno()
+else:
+    outputfd = os.open(output, os.O_WRONLY)
+
+mac=""
+
+# look for a mac= option in the options passed in
+# should do this properly using getopt?
+for arg in sys.argv[1:]:
+    if macre.match(arg):
+        mac=arg.split('=')[1]
+        print "pypxeboot: requesting info for MAC address "+mac+""
+        break
+
+if mac == "":
+    print "pypxeboot: Didn't get a MAC address, dying"
+    sys.exit(1)
+
+# run modified udhcp with specified MAC address
+udhcp_result=commands.getstatusoutput(udhcpc_command+" -n -q -s "+
+                                      udhcpc_script+" -M "+mac)
+
+if (udhcp_result[0] != 0):
+    print "pypxeboot: udhcpc failed (%s), output: %s\n" %(udhcp_result[0],
+                                                          udhcp_result[1])
+    sys.exit(1)
+
+# parse python formatted output from udhcp-executed script
+udhcplines=udhcp_result[1].split('\n')
+
+dhcpinfo={}
+
+for line in udhcplines:
+    s = line.strip()
+    f = s.split()
+
+    if s[0]=='{' and s[-1]=='}':
+        dhcpinfo=eval(s, {"__builtins__" : {}})
+        for k in dhcpinfo:
+            dhcpinfo[k]=dhcpinfo[k].strip()
+
+# run tftp client to get configuration info
+servaddr=dhcpinfo['siaddr']
+
+ipaddr=dhcpinfo['ip']
+ipaddrlist=ipaddr.split('.')
+hexip=commands.getstatusoutput("/usr/bin/gethostip -x "+ipaddr)[1]
+
+print "pypxeboot: getting cfg for IP %s (%s) from server %s" %(ipaddr,hexip,servaddr)
+
+tmpdir="/var/lib/xen/"
+
+os.chdir(tmpdir)
+commandstr="tftp -c get "+servaddr+":pxelinux.cfg/"+hexip
+#print "running command "+commandstr
+getpxeres=commands.getstatusoutput(commandstr)
+
+# check for errors in tftp output -- it doesn't use return codes properly!
+if not tftp_success(getpxeres):
+    print ("pypxeboot: error getting pxelinux cfg")
+    sys.exit(1)
+
+# read in the downloaded pxelinux cfg file
+cfgfile=open(tmpdir+hexip)
+cfglines=cfgfile.readlines()
+
+# check whether we should drop to localboot
+# XXX should really check that localboot is the default
+localbootre=re.compile("\s*localboot\w*")
+
+for line in cfglines:
+    if (localbootre.match(line)):
+        print "pypxeboot: dropping to pygrub for local boot"
+        run_pygrub()
+        sys.exit(0)
+
+# if "network" boot get kernel to local file and return the location as
+# sxp as pygrub does
+
+kernelre=re.compile("kernel*")
+appendre=re.compile("append*")
+
+# parse the pxelinux entry: add key/value pairs to
+# a dict and dump all other args to a string
+# XXX assumes there's only one entry at the moment
+# XXX need to parse properly and use default entry
+syslinux={}
+simpleargs=""
+for line in cfglines:
+    if (line[0]!='#'):
+        line=line.strip()
+        if (kernelre.match(line)):
+            (k,v)=line.split()
+            syslinux[k]=v
+        elif (appendre.match(line)):
+            havekernelargs=True
+            for entry in line[6:].split():
+                if (entry.find('=') != -1):
+                    (k,v)=entry.split('=')
+                    syslinux[k]=v
+                else:
+                    simpleargs+=entry+' '
+            
+
+# if network boot, get kernel and initrd
+# temp directory should still be the working dir
+dlres={}
+for i in ["initrd","kernel"]:
+    cmd="tftp -c get "+servaddr+":"+syslinux[i]
+    print "pypxeboot: downloading "+i+" using cmd: "+cmd
+    dlres[i]=commands.getstatusoutput(cmd)
+    if not tftp_success (dlres[i]):
+        print "pypxeboot: tftp failed for "+i+": "+dlres[i][1]
+        sys.exit(1)
+
+# format kernel and args as sxp
+# will need to get the --output option and write to that fd
+kernelname=syslinux['kernel'].split('/')[-1]
+initrdname=syslinux['initrd'].split('/')[-1]
+
+sxp="linux (kernel %s)" %(tmpdir+kernelname,)
+
+if 'initrd' in syslinux:
+    sxp+="(ramdisk %s)" % (tmpdir+initrdname,)
+if havekernelargs:
+    sxp+="(args '"
+    for arg in syslinux:
+        if arg != 'kernel' and arg != 'initrd':
+            sxp+=arg+"="+syslinux[arg]+' '
+    sxp+=simpleargs
+    sxp=sxp[0:-1]        
+    sxp+="'"
+sxp+=")"        
+
+sys.stdout.flush()
+os.write(outputfd,sxp)
diff -r 01ec7dba9ff8 -r 7f1a38c5c086 tools/pypxeboot/udhcp_usermac.patch
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/tools/pypxeboot/udhcp_usermac.patch	Mon Feb 05 11:07:21 2007 +0000
@@ -0,0 +1,107 @@
+diff -u udhcp-0.9.8/dhcpc.c udhcp-0.9.8.mod/dhcpc.c
+--- udhcp-0.9.8/dhcpc.c	2002-10-19 02:10:43.000000000 +0100
++++ udhcp-0.9.8.mod/dhcpc.c	2007-02-02 14:41:11.000000000 +0000
+@@ -67,6 +67,7 @@
+ 	foreground: 0,
+ 	quit_after_lease: 0,
+ 	background_if_no_lease: 0,
++	userarp: 0,
+ 	interface: "eth0",
+ 	pidfile: NULL,
+ 	script: DEFAULT_SCRIPT,
+@@ -95,6 +96,7 @@
+ "  -r, --request=IP                IP address to request (default: none)\n"
+ "  -s, --script=file               Run file at dhcp events (default:\n"
+ "                                  " DEFAULT_SCRIPT ")\n"
++"  -M, --mac=MAC                   MAC address to use instead of HW MAC\n"
+ "  -v, --version                   Display version\n"
+ 	);
+ 	exit(0);
+@@ -132,6 +134,7 @@
+ 		state = INIT_SELECTING;
+ 		break;
+ 	case INIT_SELECTING:
++		break;
+ 	}
+ 
+ 	/* start things over */
+@@ -207,6 +210,7 @@
+ #endif
+ {
+ 	unsigned char *temp, *message;
++	unsigned char hwmac[6];
+ 	unsigned long t1 = 0, t2 = 0, xid = 0;
+ 	unsigned long start = 0, lease;
+ 	fd_set rfds;
+@@ -233,14 +237,15 @@
+ 		{"request",	required_argument,	0, 'r'},
+ 		{"script",	required_argument,	0, 's'},
+ 		{"version",	no_argument,		0, 'v'},
++		{"mac",	        required_argument,	0, 'M'},
+ 		{"help",	no_argument,		0, '?'},
+ 		{0, 0, 0, 0}
+ 	};
+ 
+ 	/* get options */
+ 	while (1) {
+-		int option_index = 0;
+-		c = getopt_long(argc, argv, "c:fbH:h:i:np:qr:s:v", arg_options, &option_index);
++		int option_index = 0, nrmacfields=0;
++		c = getopt_long(argc, argv, "c:fbH:h:i:np:qr:s:v:M:", arg_options, &option_index);
+ 		if (c == -1) break;
+ 		
+ 		switch (c) {
+@@ -290,6 +295,16 @@
+ 			printf("udhcpcd, version %s\n\n", VERSION);
+ 			exit_client(0);
+ 			break;
++                case 'M':                      
++			nrmacfields=sscanf(optarg,"%x:%x:%x:%x:%x:%x",
++                                           (unsigned int *)&client_config.arp[0],
++                                           (unsigned int *)&client_config.arp[1],
++                                           (unsigned int *)&client_config.arp[2],
++                                           (unsigned int *)&client_config.arp[3],
++                                           (unsigned int *)&client_config.arp[4],
++                                           (unsigned int *)&client_config.arp[5]);
++                        if (nrmacfields == 6) client_config.userarp=1;
++                        break;
+ 		default:
+ 			show_usage();
+ 		}
+@@ -302,9 +317,11 @@
+ 	pidfile_write_release(pid_fd);
+ 
+ 	if (read_interface(client_config.interface, &client_config.ifindex, 
+-			   NULL, client_config.arp) < 0)
++	         	   NULL, hwmac) < 0)
+ 		exit_client(1);
+-		
++
++	if (!(client_config.userarp)) memcpy(client_config.arp, hwmac, 6);
++
+ 	if (!client_config.clientid) {
+ 		client_config.clientid = xmalloc(6 + 3);
+ 		client_config.clientid[OPT_CODE] = DHCP_CLIENT_ID;
+diff -u udhcp-0.9.8/dhcpc.h udhcp-0.9.8.mod/dhcpc.h
+--- udhcp-0.9.8/dhcpc.h	2002-09-20 21:36:15.000000000 +0100
++++ udhcp-0.9.8.mod/dhcpc.h	2007-02-02 14:13:52.000000000 +0000
+@@ -19,6 +19,7 @@
+ 	char quit_after_lease;		/* Quit after obtaining lease */
+ 	char abort_if_no_lease;		/* Abort if no lease */
+ 	char background_if_no_lease;	/* Fork to background if no lease */
++	char userarp;                   /* Did the user give us an ARP address */
+ 	char *interface;		/* The name of the interface to use */
+ 	char *pidfile;			/* Optionally store the process ID */
+ 	char *script;			/* User script to run at dhcp events */
+diff -u udhcp-0.9.8/README.udhcpc udhcp-0.9.8.mod/README.udhcpc
+--- udhcp-0.9.8/README.udhcpc	2002-10-31 18:02:09.000000000 +0000
++++ udhcp-0.9.8.mod/README.udhcpc	2007-02-02 14:12:47.000000000 +0000
+@@ -24,6 +24,7 @@
+ -r, --request=IP                IP address to request (default: none)
+ -s, --script=file               Run file at dhcp events (default:
+                                 /usr/share/udhcpc/default.script)
++-M, --mac=MAC                   MAC address to use instead of HW MAC
+ -v, --version                   Display version
+ 
+ 
+Common subdirectories: udhcp-0.9.8/samples and udhcp-0.9.8.mod/samples

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Re: [PATCH] pypxeboot bootloader

[Tim Deegan]

Hi, 

At 11:13 +0000 on 05 Feb (1170673998), Stephen Childs wrote:
> As promised on Friday here is the patch for the pypxeboot bootloader. It 
> would be great if someone could try it out and give me some feedback.

First impressions: this looks really useful but has a few rough edges
that need to be knocked off.  (I haven't had a chance to try this on a
real machine yet.)

> +for line in udhcplines:
> +    s = line.strip()
> +    f = s.split()
> +
> +    if s[0]=='{' and s[-1]=='}':
> +        dhcpinfo=eval(s, {"__builtins__" : {}})
> +        for k in dhcpinfo:
> +            dhcpinfo[k]=dhcpinfo[k].strip()

Executing the results of programs scares me.  Could you just parse it?

> +ipaddr=dhcpinfo['ip']
> +ipaddrlist=ipaddr.split('.')
> +hexip=commands.getstatusoutput("/usr/bin/gethostip -x "+ipaddr)[1]

This requires syslinux to be installed on the Xen host, and isn't 
hard to do by hand: "%2.2x%2.2x%2.2x%2.2x" % tuple(map (int, ipaddrlist))
(I'm sure more heavyweight python hackers can correct my style.)

> +tmpdir="/var/lib/xen/"
> +
> +os.chdir(tmpdir)
> +commandstr="tftp -c get "+servaddr+":pxelinux.cfg/"+hexip
> +#print "running command "+commandstr
> +getpxeres=commands.getstatusoutput(commandstr)

You'll need to be more careful with temporary file names -- here at
least the filename is unique to the guest (we hope!) but for the kernel
etc., two boots could clash.  Also, you don't seem to remove the
downloaded config files.

Cheers,

Tim.

-- 
Tim Deegan <Tim.Deegan@xensource.com>, XenSource UK Limited
Registered office c/o EC2Y 5EB, UK; company number 05334508

Re: [PATCH] pypxeboot bootloader

[Ewan Mellor]

On Mon, Feb 05, 2007 at 05:36:12PM +0000, Tim Deegan wrote:

> Hi, 
> 
> At 11:13 +0000 on 05 Feb (1170673998), Stephen Childs wrote:
> > As promised on Friday here is the patch for the pypxeboot bootloader. It 
> > would be great if someone could try it out and give me some feedback.
> 
> First impressions: this looks really useful but has a few rough edges
> that need to be knocked off.  (I haven't had a chance to try this on a
> real machine yet.)
> 
> > +for line in udhcplines:
> > +    s = line.strip()
> > +    f = s.split()
> > +
> > +    if s[0]=='{' and s[-1]=='}':
> > +        dhcpinfo=eval(s, {"__builtins__" : {}})
> > +        for k in dhcpinfo:
> > +            dhcpinfo[k]=dhcpinfo[k].strip()
> 
> Executing the results of programs scares me.  Could you just parse it?
> 
> > +ipaddr=dhcpinfo['ip']
> > +ipaddrlist=ipaddr.split('.')
> > +hexip=commands.getstatusoutput("/usr/bin/gethostip -x "+ipaddr)[1]
> 
> This requires syslinux to be installed on the Xen host, and isn't 
> hard to do by hand: "%2.2x%2.2x%2.2x%2.2x" % tuple(map (int, ipaddrlist))
> (I'm sure more heavyweight python hackers can correct my style.)

(4 * "%2.2x") % tuple(map (int, ipaddrlist))

or

"".join(["%2.2x" % int(i) for i in ipaddrlist])

Both are pleasingly arcane...

Ewan.

Re: [PATCH] pypxeboot bootloader

[Stephen Childs]

Tim Deegan wrote:
> First impressions: this looks really useful but has a few rough edges
> that need to be knocked off.  (I haven't had a chance to try this on a
> real machine yet.)

I absolutely agree, this was the first working version and I was aware 
there were nasties in it.

>> +for line in udhcplines:
>> +    s = line.strip()
>> +    f = s.split()
>> +
>> +    if s[0]=='{' and s[-1]=='}':
>> +        dhcpinfo=eval(s, {"__builtins__" : {}})
>> +        for k in dhcpinfo:
>> +            dhcpinfo[k]=dhcpinfo[k].strip()
> 
> Executing the results of programs scares me.  Could you just parse it?

Yes quite. Sorry that was cut-and-paste code so I didn't think about it 
enough. Will rewrite.

>> +ipaddr=dhcpinfo['ip']
>> +ipaddrlist=ipaddr.split('.')
>> +hexip=commands.getstatusoutput("/usr/bin/gethostip -x "+ipaddr)[1]
> This requires syslinux to be installed on the Xen host, and isn't 
> hard to do by hand: "%2.2x%2.2x%2.2x%2.2x" % tuple(map (int, ipaddrlist))
> (I'm sure more heavyweight python hackers can correct my style.)

Yes of course I'll change that.

>> +tmpdir="/var/lib/xen/"
>> +
>> +os.chdir(tmpdir)
>> +commandstr="tftp -c get "+servaddr+":pxelinux.cfg/"+hexip
>> +#print "running command "+commandstr
>> +getpxeres=commands.getstatusoutput(commandstr)
> 
> You'll need to be more careful with temporary file names -- here at
> least the filename is unique to the guest (we hope!) but for the kernel
> etc., two boots could clash.  Also, you don't seem to remove the
> downloaded config files.

Yes that all needs tidying up. Unfortunately the version of tftp I was 
using didn't actually support "get <remote-file> <local-file>" as 
advertised which I was initially going to use. I'll have to download to 
the filename supplied by the server then move to a tmpfile.

On the subject of removing files yes of course I'll remove the config 
files. Comparing with pygrub, that seems to leave kernels and initrds 
clogging up /var/lib/xen, and I suppose I'll end up doing the same. I 
suppose you could set up tmpwatch to clean it up, but it still seems a bit 
messy.

Expect a new patch soon ...

Stephen
-- 
Dr. Stephen Childs,
Research Fellow, EGEE Project,    phone:                    +353-1-8961797
Computer Architecture Group,      email:        Stephen.Childs @ cs.tcd.ie
Trinity College Dublin, Ireland   web: http://www.cs.tcd.ie/Stephen.Childs

RE: [PATCH] pypxeboot bootloader

[Ian Pratt]

> Yes that all needs tidying up. Unfortunately the version of tftp I was
> using didn't actually support "get <remote-file> <local-file>" as
> advertised which I was initially going to use. I'll have to download
to
> the filename supplied by the server then move to a tmpfile.

tftp-hpa as supplied with FC3 seems to work: "tftp tftp-serv -c get foo
/tmp/bar"

Incidentally, what do you do if the guest vif is not going to be on the
same bridge that dom0 eth0 is on? In practice this likely matters more
for the dhcp request than the tftp transfer.

Ian

Re: [PATCH] pypxeboot bootloader

[Tim Deegan]

Hi, 

At 14:27 +0000 on 08 Feb (1170944860), Stephen Childs wrote:
> Yes that all needs tidying up. Unfortunately the version of tftp I was 
> using didn't actually support "get <remote-file> <local-file>" as 
> advertised which I was initially going to use.

:( 

> I'll have to download to 
> the filename supplied by the server then move to a tmpfile.

How about a wrapper function that mkdirs a new randomly named
directory, does the tftp in there, and then moves the file to the
destination path and rmdirs the temp dir?

> On the subject of removing files yes of course I'll remove the config 
> files. Comparing with pygrub, that seems to leave kernels and initrds 
> clogging up /var/lib/xen, and I suppose I'll end up doing the same. I 
> suppose you could set up tmpwatch to clean it up, but it still seems a bit 
> messy.

The kernel and initrd files are actually deleted by Xend after it has
used them to boot the domain.  Somewhere way out on my todo/wish-list is
plumbing the kernel/initrd through pipes and buffers, or open fds on
unlinked files or some such...

> Expect a new patch soon ...

Great; thanks for that.  

Cheers,

Tim.

-- 
Tim Deegan <Tim.Deegan@xensource.com>, XenSource UK Limited
Registered office c/o EC2Y 5EB, UK; company number 05334508

Re: [PATCH] pypxeboot bootloader

[Stephen Childs]

[-- Attachment #1: Type: text/plain, Size: 1155 bytes --]

Ian Pratt wrote:
> tftp-hpa as supplied with FC3 seems to work: "tftp tftp-serv -c get foo
> /tmp/bar"

Yes and tftp version 0.43 from 
http://www.kernel.org/pub/software/network/tftp/ works too. I was using a 
much older one before so everything should be OK as long as people use a 
recent version. I've put it in the README.

I've attached a fresh patch that addresses this and the other issues you 
raised, Tim.

> Incidentally, what do you do if the guest vif is not going to be on the
> same bridge that dom0 eth0 is on? In practice this likely matters more
> for the dhcp request than the tftp transfer.
Could you explain what the problem would be? Do you mean that the DHCP 
server might not be set up to serve requests from the dom0's subnet? To be 
honest I hadn't thought that much about more complex setups -- as it is 
there are embedded assumptions about the way pxelinux is set up.

Stephen
-- 
Dr. Stephen Childs,
Research Fellow, EGEE Project,    phone:                    +353-1-8961797
Computer Architecture Group,      email:        Stephen.Childs @ cs.tcd.ie
Trinity College Dublin, Ireland   web: http://www.cs.tcd.ie/Stephen.Childs

[-- Attachment #2: childss_pypxeboot_revised_patch --]
[-- Type: text/plain, Size: 15389 bytes --]

# HG changeset patch
# User childss@tg23.testgrid
# Date 1170952399 0
# Node ID 4cf16fd716cf1dff0859afda632f6cf922c35dfa
# Parent  780f097b54c5f9161f7c6cf3f86b2bb72cc43587
pypxeboot, a PXE-like bootloader for getting configuration
and kernel images for Domain Us.
Signed-off-by: Stephen Childs <childss@cs.tcd.ie>

diff -r 780f097b54c5 -r 4cf16fd716cf tools/pypxeboot/README
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/tools/pypxeboot/README	Thu Feb 08 16:33:19 2007 +0000
@@ -0,0 +1,44 @@
+pypxeboot is a bootloader for xen that simulates PXE behaviour. It runs on 
+Domain 0 as part of the domain creation process and downloads boot information
+from a previously-configured PXELinux server using TFTP.
+
+pypxeboot requires the following external programs:
+
+1) A patched version of udhcp 0.9.8 (http://udhcp.busybox.net/) that supports 
+a user-specified MAC address. The patch is udhcp_usermac.patch, available
+in this distribution. There is also a script needed to output information
+received from the DHCP server. This is called outputpy.udhcp.sh and
+should be installed at /usr/share/udhcpc/
+
+2) The tftp client program (source and RPMs available at
+http://www.kernel.org/pub/software/network/tftp/). N.B. pypxeboot
+has been tested with version 0.43 of tftp.
+
+To use pypxeboot, add the following lines to your Xen domain configuration
+file:
+
+bootloader="/usr/bin/pypxeboot"
+bootargs=vif[0]
+
+If the pxelinux.cfg entry is set to localboot you should see output like this:
+
+[root@tg23 pypxeboot]# xm create  cagnode50-slc308
+Using config file "/etc/xen/cagnode50-slc308".
+pypxeboot: requesting info for MAC address AA:00:86:e2:35:72
+pypxeboot: getting cfg for IP 134.226.53.114 (86E23572) from server 192.168.12.1
+pypxeboot: dropping to pygrub for local boot
+Going to boot Scientific Linux CERN Xen DomU-xenU (2.4.21-47.0.1.EL.cernxenU)
+  kernel: /vmlinuz-2.4.21-47.0.1.EL.cernxenU
+  initrd: /initrd-2.4.21-47.0.1.EL.cernxenU.img
+
+and something like this if the pxelinux.cfg entry specifies a network boot:
+
+[root@tg23 pypxeboot]# xm create  cagnode50-slc308
+Using config file "/etc/xen/cagnode50-slc308".
+pypxeboot: requesting info for MAC address AA:00:86:e2:35:72
+pypxeboot: getting cfg for IP 134.226.53.114 (86E23572) from server 192.168.12.1
+pypxeboot: downloading initrd using cmd: tftp -c get 192.168.12.1:slc308_i386_xen/initrd.img
+pypxeboot: downloading kernel using cmd: tftp -c get 192.168.12.1:slc308_i386_xen/vmlinuz
+Started domain cagnode50
+
+The kernel and initrd on the tftp server need to be XenLinux images.
diff -r 780f097b54c5 -r 4cf16fd716cf tools/pypxeboot/outputpy.udhcp.sh
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/tools/pypxeboot/outputpy.udhcp.sh	Thu Feb 08 16:33:19 2007 +0000
@@ -0,0 +1,44 @@
+#!/bin/sh
+#
+# outputpy.udhcp.sh: a simple script called by udhcpc when a lease is
+# obtained. The script takes information passed by udhcpc as environment
+# variables and outputs it formatted as key/value pairs. Only the variables
+# needed by pypxeboot are currently printed: others are listed in comments
+# for reference.
+# Copyright 2007 Trinity College Dublin
+# Author: Stephen Childs <childss@cs.tcd.ie>
+
+# we only need to process "bound" events
+if [ "$1" == "bound" ]; then
+echo ip=$ip
+echo siaddr=$siaddr
+echo sname=$sname
+echo boot_file=$boot_file
+echo subnet=$subnet
+echo timezone=$timezone
+echo router=$router
+echo bootfile=$bootfile #        - The bootfile name
+fi
+exit 0
+
+#        timesvr         - A list of time servers
+#        namesvr 
+#        dns  
+#        logsvr          - A list of MIT-LCS UDP log servers
+#        cookiesvr       - A list of RFC 865 cookie servers
+#        lprsvr          - A list of LPR servers
+#        hostname        - The assigned hostname
+#        bootsize        - The length in 512 octect blocks of the bootfile
+#        domain          - The domain name of the network
+#        swapsvr         - The IP address of the client's swap server
+#        rootpath        - The path name of the client's root disk
+#        ipttl           - The TTL to use for this network
+#        mtu             - The MTU to use for this network
+#        broadcast       - The broadcast address for this network
+#        ntpsrv          - A list of NTP servers
+#        wins            - A list of WINS servers
+#        lease           - The lease time, in seconds
+#        dhcptype        - DHCP message type (safely ignored)
+#        serverid        - The IP of the server
+#        message         - Reason for a DHCPNAK
+#        tftp            - The TFTP server name
diff -r 780f097b54c5 -r 4cf16fd716cf tools/pypxeboot/pypxeboot
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/tools/pypxeboot/pypxeboot	Thu Feb 08 16:33:19 2007 +0000
@@ -0,0 +1,209 @@
+#!/usr/bin/python
+#
+# pypxeboot - simple python-based bootloader to fake PXE booting for Xen DomUs
+# Uses a modified version of udhcpc that allows MAC address to be passed on
+# the command line. Also uses tftp client to download configuration and images
+#
+# Copyright 2007 Trinity College Dublin
+# Stephen Childs <childss@cs.tcd.ie>
+#
+# This software may be freely redistributed under the terms of the GNU
+# general public license.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, write to the Free Software
+# Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+#
+
+import commands,sys,re,os,getopt,tempfile,shutil
+
+udhcpc_command="/usr/bin/udhcpc"
+udhcpc_script="/usr/share/udhcpc/outputpy.udhcp.sh"
+havekernelargs=False
+
+def run_pygrub():
+    arglist=[]
+    for arg in sys.argv[1:]:
+        if not (macre.match(arg)):
+            arglist.append(arg)
+
+    program="/usr/bin/pygrub"
+
+    os.execvp(program, (program,) +  tuple(arglist))
+
+def tftp_success(statusoutput):
+    errorre=re.compile("Error*")
+    if errorre.match(statusoutput[1]):
+        return False
+    else:
+        return True
+
+# get arguments from calling program -- most important is MAC address
+macre=re.compile("mac*=*",re.IGNORECASE)
+outputre=re.compile("--output*",re.IGNORECASE)
+
+def usage():
+    print >> sys.stderr, "Usage: %s [-q|--quiet] [--output=] [--entry=] mac= <image>" %(sys.argv[0],)
+
+try:
+    opts, args = getopt.gnu_getopt(sys.argv[1:], 'qh::',
+                                   ["quiet", "help", "output=", "entry=", "mac=",
+                                    "isconfig"])
+except getopt.GetoptError:
+    usage()
+    sys.exit(1)
+
+if len(args) < 1:
+    usage()
+    sys.exit(1)
+
+output = None
+
+for o, a in opts:
+    if o in  ("--output",):
+        output = a
+
+if output is None or output == "-":
+    outputfd = sys.stdout.fileno()
+else:
+    outputfd = os.open(output, os.O_WRONLY)
+
+mac=""
+
+# look for a mac= option in the options passed in
+# should do this properly using getopt?
+for arg in sys.argv[1:]:
+    if macre.match(arg):
+        mac=arg.split('=')[1]
+        print "pypxeboot: requesting info for MAC address "+mac+""
+        break
+
+if mac == "":
+    print "pypxeboot: Didn't get a MAC address, dying"
+    sys.exit(1)
+
+# run modified udhcp with specified MAC address
+udhcp_result=commands.getstatusoutput(udhcpc_command+" -n -q -s "+
+                                      udhcpc_script+" -M "+mac)
+
+if (udhcp_result[0] != 0):
+    print "pypxeboot: udhcpc failed (%s), output: %s\n" %(udhcp_result[0],
+                                                          udhcp_result[1])
+    sys.exit(1)
+
+# parse output from udhcp-executed script (looking for key=value
+# pairs)
+udhcplines=udhcp_result[1].split('\n')
+
+dhcpinfo={}
+
+for line in udhcplines:
+    s = line.strip()
+    if (s.find('=') != -1):
+        f=s.split('=')
+        dhcpinfo[f[0]]=f[1]
+
+# run tftp client to get configuration info
+servaddr=dhcpinfo['siaddr']
+
+ipaddr=dhcpinfo['ip']
+ipaddrlist=ipaddr.split('.')
+hexip=(4 * "%2.2X") % tuple(map (int, ipaddrlist))
+
+print "pypxeboot: getting cfg for IP %s (%s) from server %s" %(ipaddr,hexip,servaddr)
+
+tmpdir="/var/lib/xen/"
+
+os.chdir(tmpdir)
+commandstr="tftp "+servaddr+" -c get pxelinux.cfg/"+hexip
+#print "running command "+commandstr
+getpxeres=commands.getstatusoutput(commandstr)
+
+# check for errors in tftp output -- it doesn't use return codes properly!
+if not tftp_success(getpxeres):
+    print ("pypxeboot: error getting pxelinux cfg")
+    sys.exit(1)
+
+# read in the downloaded pxelinux cfg file
+cfgfilename=tmpdir+hexip
+cfgfile=open(cfgfilename)
+cfglines=cfgfile.readlines()
+
+# check whether we should drop to localboot
+# XXX should really check that localboot is the default
+localbootre=re.compile("\s*localboot\w*")
+
+for line in cfglines:
+    if (localbootre.match(line)):
+        print "pypxeboot: dropping to pygrub for local boot"
+        run_pygrub()
+        sys.exit(0)
+
+# remove downloaded config file
+cfgfile.close()
+os.remove(cfgfilename)
+
+# if "network" boot get kernel to local file and return the location as
+# sxp as pygrub does
+
+kernelre=re.compile("kernel*")
+appendre=re.compile("append*")
+
+# parse the pxelinux entry: add key/value pairs to
+# a dict and dump all other args to a string
+# XXX assumes there's only one entry at the moment
+# XXX need to parse properly and use default entry
+syslinux={}
+simpleargs=""
+for line in cfglines:
+    if (line[0]!='#'):
+        line=line.strip()
+        if (kernelre.match(line)):
+            (k,v)=line.split()
+            syslinux[k]=v
+        elif (appendre.match(line)):
+            havekernelargs=True
+            for entry in line[6:].split():
+                if (entry.find('=') != -1):
+                    (k,v)=entry.split('=')
+                    syslinux[k]=v
+                else:
+                    simpleargs+=entry+' '
+            
+
+# if network boot, get kernel and initrd
+# temp directory should still be the working dir
+dlres={}
+tmpimages={}
+for i in ["initrd","kernel"]:
+    (tfd,tfn)=tempfile.mkstemp(prefix=i+".", dir=tmpdir)
+    cmd="tftp "+servaddr+" -c get "+syslinux[i]+" "+tfn
+    tmpimages[i]=tfn
+    print "pypxeboot: downloading "+i+" using cmd: "+cmd
+    dlres[i]=commands.getstatusoutput(cmd)
+    if not tftp_success (dlres[i]):
+        print "pypxeboot: tftp failed for "+i+": "+dlres[i][1]
+        sys.exit(1)
+
+
+# format kernel and args as sxp
+# will need to get the --output option and write to that fd
+kernelname=syslinux['kernel'].split('/')[-1]
+initrdname=syslinux['initrd'].split('/')[-1]
+
+sxp="linux (kernel %s)" %(tmpimages['kernel'],)
+
+if 'initrd' in syslinux:
+    sxp+="(ramdisk %s)" % (tmpimages['initrd'],)
+if havekernelargs:
+    sxp+="(args '"
+    for arg in syslinux:
+        if arg != 'kernel' and arg != 'initrd':
+            sxp+=arg+"="+syslinux[arg]+' '
+    sxp+=simpleargs
+    sxp=sxp[0:-1]       # remove trailing space
+    sxp+="'"
+sxp+=")"        
+
+sys.stdout.flush()
+os.write(outputfd,sxp)
diff -r 780f097b54c5 -r 4cf16fd716cf tools/pypxeboot/udhcp_usermac.patch
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/tools/pypxeboot/udhcp_usermac.patch	Thu Feb 08 16:33:19 2007 +0000
@@ -0,0 +1,107 @@
+diff -u udhcp-0.9.8/dhcpc.c udhcp-0.9.8.mod/dhcpc.c
+--- udhcp-0.9.8/dhcpc.c	2002-10-19 02:10:43.000000000 +0100
++++ udhcp-0.9.8.mod/dhcpc.c	2007-02-02 14:41:11.000000000 +0000
+@@ -67,6 +67,7 @@
+ 	foreground: 0,
+ 	quit_after_lease: 0,
+ 	background_if_no_lease: 0,
++	userarp: 0,
+ 	interface: "eth0",
+ 	pidfile: NULL,
+ 	script: DEFAULT_SCRIPT,
+@@ -95,6 +96,7 @@
+ "  -r, --request=IP                IP address to request (default: none)\n"
+ "  -s, --script=file               Run file at dhcp events (default:\n"
+ "                                  " DEFAULT_SCRIPT ")\n"
++"  -M, --mac=MAC                   MAC address to use instead of HW MAC\n"
+ "  -v, --version                   Display version\n"
+ 	);
+ 	exit(0);
+@@ -132,6 +134,7 @@
+ 		state = INIT_SELECTING;
+ 		break;
+ 	case INIT_SELECTING:
++		break;
+ 	}
+ 
+ 	/* start things over */
+@@ -207,6 +210,7 @@
+ #endif
+ {
+ 	unsigned char *temp, *message;
++	unsigned char hwmac[6];
+ 	unsigned long t1 = 0, t2 = 0, xid = 0;
+ 	unsigned long start = 0, lease;
+ 	fd_set rfds;
+@@ -233,14 +237,15 @@
+ 		{"request",	required_argument,	0, 'r'},
+ 		{"script",	required_argument,	0, 's'},
+ 		{"version",	no_argument,		0, 'v'},
++		{"mac",	        required_argument,	0, 'M'},
+ 		{"help",	no_argument,		0, '?'},
+ 		{0, 0, 0, 0}
+ 	};
+ 
+ 	/* get options */
+ 	while (1) {
+-		int option_index = 0;
+-		c = getopt_long(argc, argv, "c:fbH:h:i:np:qr:s:v", arg_options, &option_index);
++		int option_index = 0, nrmacfields=0;
++		c = getopt_long(argc, argv, "c:fbH:h:i:np:qr:s:v:M:", arg_options, &option_index);
+ 		if (c == -1) break;
+ 		
+ 		switch (c) {
+@@ -290,6 +295,16 @@
+ 			printf("udhcpcd, version %s\n\n", VERSION);
+ 			exit_client(0);
+ 			break;
++                case 'M':                      
++			nrmacfields=sscanf(optarg,"%x:%x:%x:%x:%x:%x",
++                                           (unsigned int *)&client_config.arp[0],
++                                           (unsigned int *)&client_config.arp[1],
++                                           (unsigned int *)&client_config.arp[2],
++                                           (unsigned int *)&client_config.arp[3],
++                                           (unsigned int *)&client_config.arp[4],
++                                           (unsigned int *)&client_config.arp[5]);
++                        if (nrmacfields == 6) client_config.userarp=1;
++                        break;
+ 		default:
+ 			show_usage();
+ 		}
+@@ -302,9 +317,11 @@
+ 	pidfile_write_release(pid_fd);
+ 
+ 	if (read_interface(client_config.interface, &client_config.ifindex, 
+-			   NULL, client_config.arp) < 0)
++	         	   NULL, hwmac) < 0)
+ 		exit_client(1);
+-		
++
++	if (!(client_config.userarp)) memcpy(client_config.arp, hwmac, 6);
++
+ 	if (!client_config.clientid) {
+ 		client_config.clientid = xmalloc(6 + 3);
+ 		client_config.clientid[OPT_CODE] = DHCP_CLIENT_ID;
+diff -u udhcp-0.9.8/dhcpc.h udhcp-0.9.8.mod/dhcpc.h
+--- udhcp-0.9.8/dhcpc.h	2002-09-20 21:36:15.000000000 +0100
++++ udhcp-0.9.8.mod/dhcpc.h	2007-02-02 14:13:52.000000000 +0000
+@@ -19,6 +19,7 @@
+ 	char quit_after_lease;		/* Quit after obtaining lease */
+ 	char abort_if_no_lease;		/* Abort if no lease */
+ 	char background_if_no_lease;	/* Fork to background if no lease */
++	char userarp;                   /* Did the user give us an ARP address */
+ 	char *interface;		/* The name of the interface to use */
+ 	char *pidfile;			/* Optionally store the process ID */
+ 	char *script;			/* User script to run at dhcp events */
+diff -u udhcp-0.9.8/README.udhcpc udhcp-0.9.8.mod/README.udhcpc
+--- udhcp-0.9.8/README.udhcpc	2002-10-31 18:02:09.000000000 +0000
++++ udhcp-0.9.8.mod/README.udhcpc	2007-02-02 14:12:47.000000000 +0000
+@@ -24,6 +24,7 @@
+ -r, --request=IP                IP address to request (default: none)
+ -s, --script=file               Run file at dhcp events (default:
+                                 /usr/share/udhcpc/default.script)
++-M, --mac=MAC                   MAC address to use instead of HW MAC
+ -v, --version                   Display version
+ 
+ 
+Common subdirectories: udhcp-0.9.8/samples and udhcp-0.9.8.mod/samples

[-- Attachment #3: Type: text/plain, Size: 138 bytes --]

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RE: [PATCH] pypxeboot bootloader

[Ian Pratt]

> > Incidentally, what do you do if the guest vif is not going to be on
the
> > same bridge that dom0 eth0 is on? In practice this likely matters
more
> > for the dhcp request than the tftp transfer.
>
> Could you explain what the problem would be? Do you mean that the DHCP
> server might not be set up to serve requests from the dom0's subnet?
To be
> honest I hadn't thought that much about more complex setups -- as it
is
> there are embedded assumptions about the way pxelinux is set up.

I think we should at least try and send the dhcp request out on the
bridge that the guest's first VIF is going to attach to -- it might be
on an entirely different VLAN or even physical network from dom0.

Possibly it will work just to set the bridge as the interface that the
raw socket is bound to when sending the dhcp request. 


Ian

Re: [PATCH] pypxeboot bootloader

[Tim Deegan]

At 16:36 +0000 on 08 Feb (1170952573), Stephen Childs wrote:
> I've attached a fresh patch that addresses this and the other issues you 
> raised, Tim.

Thanks.  That looks much better -- I think we should use mkstemp for the
config files too, if possible.

Is udhcp still actively maintained?  I wonder if we can get the
mac-address patch in upstream; otherwise we might have to bring the 
client source into our tree.

The other option (and it may end up being necesary to address Ian's
point about physical NICs) would be to steal the guest's vif for the
dhcp'ing, since we know the guest won't be using it yet.  I haven't
looked in detail at the plumbing of that, though.

Cheers,

Tim.

-- 
Tim Deegan <Tim.Deegan@xensource.com>, XenSource UK Limited
Registered office c/o EC2Y 5EB, UK; company number 05334508

Re: [PATCH] pypxeboot bootloader

[Stephen Childs]

Tim Deegan wrote:
> At 16:36 +0000 on 08 Feb (1170952573), Stephen Childs wrote:
>> I've attached a fresh patch that addresses this and the other issues you 
>> raised, Tim.
> 
> Thanks.  That looks much better -- I think we should use mkstemp for the
> config files too, if possible.

OK I will try and have a look at that (or you're welcome to!)

> Is udhcp still actively maintained?  I wonder if we can get the
> mac-address patch in upstream; otherwise we might have to bring the 
> client source into our tree.

I've had no response to a patch I submitted and the last release was in 
2002 so maybe we will have to do that for now.

> The other option (and it may end up being necesary to address Ian's
> point about physical NICs) would be to steal the guest's vif for the
> dhcp'ing, since we know the guest won't be using it yet.  I haven't
> looked in detail at the plumbing of that, though.

That sounds like a better solution in the long-term. Hopefully the 
existing approach already provides enough functionality to be useful to 
people in the short-term though.

Stephen
-- 
Dr. Stephen Childs,
Research Fellow, EGEE Project,    phone:                    +353-1-8961797
Computer Architecture Group,      email:        Stephen.Childs @ cs.tcd.ie
Trinity College Dublin, Ireland   web: http://www.cs.tcd.ie/Stephen.Childs

Re: [PATCH] pypxeboot bootloader

[Daniel Miles]

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First off, thanks for all the work, Stephen. This is a useful feature.

I'm trying to test it, without much success. I've followed the instructions on 
https://www.cs.tcd.ie/Stephen.Childs/pypxeboot/ but when I xm create the 
machine, it just hangs on: Using config file "/etc/xen/testU1.cfg".

I don't even get any output if I put in frivolous print statements in 
pypxeboot before anything else happens.

How does xm actually invoke bootloaders? What might be happening here?

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RE: [PATCH] pypxeboot bootloader

[Ian Pratt]

> First off, thanks for all the work, Stephen. This is a useful feature.
> 
> I'm trying to test it, without much success. I've followed the
> instructions on
> https://www.cs.tcd.ie/Stephen.Childs/pypxeboot/ but when I xm create
> the
> machine, it just hangs on: Using config file "/etc/xen/testU1.cfg".
> 
> I don't even get any output if I put in frivolous print statements in
> pypxeboot before anything else happens.
> 
> How does xm actually invoke bootloaders? What might be happening here?

Not sure why its not working, but it would be good to get this patch
dusted off and made a bit more general.

The biggest problem with it is that it assumes that dom0's eth0
interface is on the same bridged network as where the guest's virtual
NIC will end up. This often won't be the case.

We could fix this quite easily, using the '-i' option to udhcp to point
to the backend vif. 

NB: Stephen: at one point does pypxeboot run? After the vifX.Y is
created and put on the right bridge? If so, this should be a trivial
change.

The other problem is that we then use dom0's default IP address to do
the tftp. Again, this would best be done using the guest's IP. The best
way of fixing this is probably to assign the backend vif with the
guest's IP returned from udhcp (i.e. actually allow udhcp to configure
an address on the vifX.Y interface). We can the get tftp to bind the
outgoing socket it creates to that local address when doing the
transfer. After completing, we should be sure to set the vif's IP
address back to 0.0.0.0.

Anyone up for making these modifications? I'd really like to see this
patch in mainline Xen.

Best,
Ian












 

RE: [PATCH] pypxeboot bootloader

[Stephen Childs]

> From: "Ian Pratt" <Ian.Pratt@cl.cam.ac.uk>
> Subject: RE: [Xen-devel] [PATCH] pypxeboot bootloader
> To: "Daniel Miles" <daniel.t.miles@hp.com>,

>> I'm trying to test it, without much success. I've followed the
>> instructions on
>> https://www.cs.tcd.ie/Stephen.Childs/pypxeboot/ but when I xm create
>> the
>> machine, it just hangs on: Using config file "/etc/xen/testU1.cfg".
>>
>> I don't even get any output if I put in frivolous print statements in
>> pypxeboot before anything else happens.
>>
>> How does xm actually invoke bootloaders? What might be happening here?

Does pygrub work? This will show you whether the problem is in the generic 
bootloader set up. If you get as far as executing pypxeboot, tcpdump 
should help you work out what's going on.

> Not sure why its not working, but it would be good to get this patch
> dusted off and made a bit more general.

Sorry, I haven't looked at it in a while due to other distractions. I 
haven't tested it with the latest release, so I can't comment on this 
breakage. I'm having another look at it now, but some help from people who 
understand the domain startup plumbing would speed the process up 
considerably.

> The biggest problem with it is that it assumes that dom0's eth0
> interface is on the same bridged network as where the guest's virtual
> NIC will end up. This often won't be the case.
> 
> We could fix this quite easily, using the '-i' option to udhcp to point
> to the backend vif. 
> 
> NB: Stephen: at one point does pypxeboot run? After the vifX.Y is
> created and put on the right bridge? If so, this should be a trivial
> change.

Yes, it would have been nice if it was that easy. However, it looks like 
the bootloader is called earlier than that (at least an ifconfig run from 
within the bootloader shows that nothing has been done at that stage). 
What is the sequence of events? Is it documented anywhere? (If not, it 
might be good to stick it on the wiki.) Any suggestions

> The other problem is that we then use dom0's default IP address to do
> the tftp. Again, this would best be done using the guest's IP. The best
> way of fixing this is probably to assign the backend vif with the
> guest's IP returned from udhcp (i.e. actually allow udhcp to configure
> an address on the vifX.Y interface). We can the get tftp to bind the
> outgoing socket it creates to that local address when doing the
> transfer. After completing, we should be sure to set the vif's IP
> address back to 0.0.0.0.

Yes this should all be manageable if we can sort out the sequencing of 
network/bootloader setup.

> Anyone up for making these modifications? I'd really like to see this
> patch in mainline Xen.
If some domain startup gurus can point me in the right direction I will 
try and make these fixes. However, I don't have the spare time to do the 
digging around myself unfortunately.


Stephen
-- 
Dr. Stephen Childs,
Research Fellow, EGEE Project,    phone:                    +353-1-8961797
Computer Architecture Group,      email:        Stephen.Childs @ cs.tcd.ie
Trinity College Dublin, Ireland   web: http://www.cs.tcd.ie/Stephen.Childs