support reading network config from kernel command line

This adds support for suppling network configuration on the
kernel command line in 2 ways:
 a.) kernel command line includes 'network-config=<base64>'
     value of that parameter is base64 encoded json (or yaml)
     it is taken as network config yaml.
     In order to save space on kernel command line, it can be
     base64 encoded gzipped json also.

 b.) ip= paired with files authored by klibc's ipconfig tool
     When network devices are brought up in the initramfs, klibc's
     ipconfig tool writes files are named /run/net-<DEVNAME>.conf.
     The best documentation available on that tool is
     /usr/share/doc/libklibc/README.ipconfig.gz.

Also changes util.get_cmdline() to return the command line of
pid 1 if it is in a container.  That is to make it consistent with
The systemd generator, and allow passing a command line to lxd,
as lxd does not mask /proc/cmdline.

2 files changed, 205 insertions, 16 deletions

diff --git a/cloudinit/net/__init__.py b/cloudinit/net/__init__.py
index 2435055b..66e0e9ee 100644
--- a/cloudinit/net/__init__.py
+++ b/cloudinit/net/__init__.py
@@ -16,10 +16,14 @@
 #   You should have received a copy of the GNU Affero General Public License
 #   along with Curtin.  If not, see <http://www.gnu.org/licenses/>.
 
+import base64
 import errno
 import glob
+import gzip
+import io
 import os
 import re
+import shlex
 
 from cloudinit import log as logging
 from cloudinit import util
@@ -283,6 +287,118 @@ def parse_net_config(path):
     return ns
 
 
+def _load_shell_content(content, add_empty=False, empty_val=None):
+    """Given shell like syntax (key=value\nkey2=value2\n) in content
+       return the data in dictionary form.  If 'add_empty' is True
+       then add entries in to the returned dictionary for 'VAR='
+       variables.  Set their value to empty_val."""
+    data = {}
+    for line in shlex.split(content):
+        key, value = line.split("=", 1)
+        if not value:
+            value = empty_val
+        if add_empty or value:
+            data[key] = value
+
+    return data
+
+
+def _klibc_to_config_entry(content, mac_addrs=None):
+    """Convert a klibc writtent shell content file to a 'config' entry
+    When ip= is seen on the kernel command line in debian initramfs
+    and networking is brought up, ipconfig will populate 
+    /run/net-<name>.cfg.
+
+    The files are shell style syntax, and examples are in the tests
+    provided here.  There is no good documentation on this unfortunately.
+
+    DEVICE=<name> is expected/required and PROTO should indicate if
+    this is 'static' or 'dhcp'.
+    """
+    
+  
+    if mac_addrs is None:
+        mac_addrs = {}
+
+    data = _load_shell_content(content)
+    try:
+        name = data['DEVICE']
+    except KeyError:
+        raise ValueError("no 'DEVICE' entry in data")
+
+    # ipconfig on precise does not write PROTO
+    proto = data.get('PROTO')
+    if not proto:
+        if data.get('filename'):
+            proto = 'dhcp'
+        else:
+            proto = 'static'
+
+    if proto not in ('static', 'dhcp'):
+        raise ValueError("Unexpected value for PROTO: %s" % proto)
+
+    iface = {
+        'type': 'physical',
+        'name': name,
+        'subnets': [],
+    }
+
+    if name in mac_addrs:
+        iface['mac_address'] = mac_addrs[name]
+
+    # originally believed there might be IPV6* values
+    for v, pre in (('ipv4', 'IPV4'),):
+        # if no IPV4ADDR or IPV6ADDR, then go on.
+        if pre + "ADDR" not in data:
+            continue
+        subnet = {'type': proto}
+
+        # these fields go right on the subnet
+        for key in ('NETMASK', 'BROADCAST', 'GATEWAY'):
+            if pre + key in data:
+                subnet[key.lower()] = data[pre + key]
+
+        dns = []
+        # handle IPV4DNS0 or IPV6DNS0
+        for nskey in ('DNS0', 'DNS1'):
+            ns = data.get(pre + nskey)
+            # verify it has something other than 0.0.0.0 (or ipv6)
+            if ns and len(ns.strip(":.0")):
+                dns.append(data[pre + nskey])
+        if dns:
+            subnet['dns_nameservers'] = dns
+            # add search to both ipv4 and ipv6, as it has no namespace
+            search = data.get('DOMAINSEARCH')
+            if search:
+                if ',' in search:
+                    subnet['dns_search'] = search.split(",")
+                else:
+                    subnet['dns_search'] = search.split()
+
+        iface['subnets'].append(subnet)
+
+    return name, iface
+
+
+def config_from_klibc_net_cfg(files=None, mac_addrs=None):
+    if files is None:
+        files = glob.glob('/run/net*.conf')
+
+    entries = []
+    names = {}
+    for cfg_file in files:
+        name, entry = _klibc_to_config_entry(util.load_file(cfg_file),
+                                             mac_addrs=mac_addrs)
+        if name in names:
+            raise ValueError(
+                "device '%s' defined multiple times: %s and %s" % (
+                    name, names[name], cfg_file))
+
+        names[name] = cfg_file
+        entries.append(entry)
+    return {'config': entries, 'version': 1}
+
+
 def render_persistent_net(network_state):
     ''' Given state, emit udev rules to map
         mac to ifname
@@ -502,6 +618,20 @@ def is_disabled_cfg(cfg):
     return cfg.get('config') == "disabled"
 
 
+def sys_netdev_info(name, field):
+    if not os.path.exists(os.path.join(SYS_CLASS_NET, name)):
+        raise OSError("%s: interface does not exist in %s" %
+                      (name, SYS_CLASS_NET))
+
+    fname = os.path.join(SYS_CLASS_NET, name, field)
+    if not os.path.exists(fname):
+        raise OSError("%s: could not find sysfs entry: %s" % (name, fname))
+    data = util.load_file(fname)
+    if data[-1] == '\n':
+        data = data[:-1]
+    return data
+
+
 def generate_fallback_config():
     """Determine which attached net dev is most likely to have a connection and
        generate network state to run dhcp on that interface"""
@@ -510,7 +640,7 @@ def generate_fallback_config():
 
     # get list of interfaces that could have connections
     invalid_interfaces = set(['lo'])
-    potential_interfaces = set(os.listdir(SYS_CLASS_NET))
+    potential_interfaces = set(get_devicelist())
     potential_interfaces = potential_interfaces.difference(invalid_interfaces)
     # sort into interfaces with carrier, interfaces which could have carrier,
     # and ignore interfaces that are definitely disconnected
@@ -518,8 +648,7 @@ def generate_fallback_config():
     possibly_connected = []
     for interface in potential_interfaces:
         try:
-            sysfs_carrier = os.path.join(SYS_CLASS_NET, interface, 'carrier')
-            carrier = int(util.load_file(sysfs_carrier).strip())
+            carrier = int(sys_netdev_info(interface, 'carrier'))
             if carrier:
                 connected.append(interface)
                 continue
@@ -529,17 +658,14 @@ def generate_fallback_config():
         # not have a carrier even though it could acquire one when brought
         # online by dhclient
         try:
-            sysfs_dormant = os.path.join(SYS_CLASS_NET, interface, 'dormant')
-            dormant = int(util.load_file(sysfs_dormant).strip())
+            dormant = int(sys_netdev_info(interface, 'dormant'))
             if dormant:
                 possibly_connected.append(interface)
                 continue
         except OSError:
             pass
         try:
-            sysfs_operstate = os.path.join(SYS_CLASS_NET, interface,
-                                           'operstate')
-            operstate = util.load_file(sysfs_operstate).strip()
+            operstate = sys_netdev_info(interface, 'operstate')
             if operstate in ['dormant', 'down', 'lowerlayerdown', 'unknown']:
                 possibly_connected.append(interface)
                 continue
@@ -562,19 +688,65 @@ def generate_fallback_config():
     else:
         name = sorted(potential_interfaces)[0]
 
-    sysfs_mac = os.path.join(SYS_CLASS_NET, name, 'address')
-    mac = util.load_file(sysfs_mac).strip()
+    mac = sys_netdev_info(name, 'address')
     target_name = name
 
     nconf['config'].append(
         {'type': 'physical', 'name': target_name,
-         'mac_address': mac, 'subnets': [{'type': 'dhcp4'}]})
+         'mac_address': mac, 'subnets': [{'type': 'dhcp'}]})
     return nconf
 
 
-def read_kernel_cmdline_config():
-    # FIXME: add implementation here
-    return None
+def _decomp_gzip(blob, strict=True):
+    # decompress blob. raise exception if not compressed unless strict=False.
+    with io.BytesIO(blob) as iobuf:
+        gzfp = None
+        try:
+            gzfp = gzip.GzipFile(mode="rb", fileobj=iobuf)
+            return gzfp.read()
+        except IOError:
+            if strict:
+                raise
+            return blob
+        finally:
+            if gzfp:
+                gzfp.close()
+
+
+def _b64dgz(b64str, gzipped="try"):
+    # decode a base64 string.  If gzipped is true, transparently uncompresss
+    # if gzipped is 'try', then try gunzip, returning the original on fail.
+    try:
+        blob = base64.b64decode(b64str)
+    except TypeError:
+        raise ValueError("Invalid base64 text: %s" % b64str)
+
+    if not gzipped:
+        return blob
+
+    return _decomp_gzip(blob, strict=gzipped != "try")
+
+
+def read_kernel_cmdline_config(files=None, mac_addrs=None, cmdline=None):
+    if cmdline is None:
+        cmdline = util.get_cmdline()
+
+    if 'network-config=' in cmdline:
+        data64 = None
+        for tok in cmdline.split():
+            if tok.startswith("network-config="):
+                data64 = tok.split("=", 1)[1]
+        if data64:
+            return util.load_yaml(_b64dgz(data64))
+
+    if 'ip=' not in cmdline:
+        return None
+
+    if mac_addrs is None:
+        mac_addrs = {k: sys_netdev_info(k, 'address')
+                     for k in get_devicelist()}
+
+    return config_from_klibc_net_cfg(files=files, mac_addrs=mac_addrs)
 
 
 # vi: ts=4 expandtab syntax=python
diff --git a/cloudinit/util.py b/cloudinit/util.py
index 20916e53..0d21e11b 100644
--- a/cloudinit/util.py
+++ b/cloudinit/util.py
@@ -80,6 +80,8 @@ CONTAINER_TESTS = (['systemd-detect-virt', '--quiet', '--container'],
                    ['running-in-container'],
                    ['lxc-is-container'])
 
+PROC_CMDLINE = None
+
 
 def decode_binary(blob, encoding='utf-8'):
     # Converts a binary type into a text type using given encoding.
@@ -1191,12 +1193,27 @@ def load_file(fname, read_cb=None, quiet=False, decode=True):
 
 def get_cmdline():
     if 'DEBUG_PROC_CMDLINE' in os.environ:
-        cmdline = os.environ["DEBUG_PROC_CMDLINE"]
+        return os.environ["DEBUG_PROC_CMDLINE"]
+
+    global PROC_CMDLINE
+    if PROC_CMDLINE is not None:
+        return PROC_CMDLINE
+
+    if is_container():
+        try:
+            contents = load_file("/proc/1/cmdline")
+            # replace nulls with space and drop trailing null
+            cmdline = contents.replace("\x00", " ")[:-1]
+        except Exception as e:
+            LOG.warn("failed reading /proc/1/cmdline: %s", e)
+            cmdline = ""
     else:
         try:
             cmdline = load_file("/proc/cmdline").strip()
         except:
             cmdline = ""
+
+    PROC_CMDLINE = cmdline
     return cmdline
 
 
@@ -1569,7 +1586,7 @@ def uptime():
     try:
         if os.path.exists("/proc/uptime"):
             method = '/proc/uptime'
-            contents = load_file("/proc/uptime").strip()
+            contents = load_file("/proc/uptime")
             if contents:
                 uptime_str = contents.split()[0]
         else: