[plugins/nbp] Implemented conditional NBP handling

The nbp plugin adds support for network boot programs in both v4 and v6
scenarios. In DHCPv6 we support bootfile URL and params, in DHPv4 we
support tftp server and file name.

Signed-off-by: Andrea Barberio <insomniac@slackware.it>

cmds/coredhcp/main.go

@@ -14,6 +14,7 @@ import (
 	_ "github.com/coredhcp/coredhcp/plugins/dns"
 	_ "github.com/coredhcp/coredhcp/plugins/file"
 	_ "github.com/coredhcp/coredhcp/plugins/lease_time"
+	_ "github.com/coredhcp/coredhcp/plugins/nbp"
 	_ "github.com/coredhcp/coredhcp/plugins/netmask"
 	_ "github.com/coredhcp/coredhcp/plugins/range"
 	_ "github.com/coredhcp/coredhcp/plugins/router"

plugins/file/plugin.go

@@ -147,24 +147,6 @@ func Handler6(req, resp dhcpv6.DHCPv6) (dhcpv6.DHCPv6, bool) {
 			},
 		},
 	})
-
-	decap, err := req.GetInnerMessage()
-	if err != nil {
-		log.Errorf("Could not decapsulate: %v", err)
-		return nil, true
-	}
-	if oro := decap.GetOption(dhcpv6.OptionORO); len(oro) > 0 {
-		for _, code := range oro[0].(*dhcpv6.OptRequestedOption).RequestedOptions() {
-			if code == dhcpv6.OptionBootfileURL {
-				// bootfile URL is requested
-				// FIXME this field should come from the configuration, not
-				// being hardcoded
-				resp.AddOption(
-					dhcpv6.OptBootFileURL("http://[2001:db8::0:1]/nbp"),
-				)
-			}
-		}
-	}
 	return resp, false
 }
 

plugins/nbp/nbp.go

@@ -0,0 +1,131 @@
+// Copyright 2018-present the CoreDHCP Authors. All rights reserved
+// This source code is licensed under the MIT license found in the
+// LICENSE file in the root directory of this source tree.
+
+// Package nbp implements handling of an NBP (Network Boot Program) using an
+// URL, e.g. http://[fe80::abcd:efff:fe12:3456]/my-nbp or tftp://10.0.0.1/my-nbp .
+// The NBP information is only added if it is requested by the client.
+//
+// Note that for DHCPv4 the URL will be split into TFTP server name (option 66)
+// and Bootfile name (option 67), so the scheme will be stripped out, and it
+// will be treated as a TFTP URL. Anything other than host name and file path
+// will be ignored (no port, no query string, etc).
+//
+// For DHCPv6 OPT_BOOTFILE_URL (option 59) is used, and the value is passed
+// unmodified. If the query string is specified and contains a "param" key,
+// its value is also passed as OPT_BOOTFILE_PARAM (option 60), so it will be
+// duplicated between option 59 and 60.
+//
+// Example usage:
+//
+// server6:
+//   - plugins:
+//     - nbp: http://[2001:db8:a::1]/nbp
+//
+// server4:
+//   - plugins:
+//     - nbp: tftp://10.0.0.254/nbp
+//
+package nbp
+
+import (
+	"fmt"
+	"net/url"
+
+	"github.com/coredhcp/coredhcp/handler"
+	"github.com/coredhcp/coredhcp/logger"
+	"github.com/coredhcp/coredhcp/plugins"
+	"github.com/insomniacslk/dhcp/dhcpv4"
+	"github.com/insomniacslk/dhcp/dhcpv6"
+)
+
+var log = logger.GetLogger("plugins/nbp")
+
+func init() {
+	plugins.RegisterPlugin("nbp", setupNBP6, setupNBP4)
+}
+
+var (
+	opt59, opt60 dhcpv6.Option
+	opt66, opt67 *dhcpv4.Option
+)
+
+func parseArgs(args ...string) (*url.URL, error) {
+	if len(args) != 1 {
+		return nil, fmt.Errorf("Exactly one argument must be passed to NBP plugin, got %d", len(args))
+	}
+	return url.Parse(args[0])
+}
+
+func setupNBP6(args ...string) (handler.Handler6, error) {
+	u, err := parseArgs(args...)
+	if err != nil {
+		return nil, err
+	}
+	opt59 = dhcpv6.OptBootFileURL(u.String())
+	params := u.Query().Get("params")
+	if params != "" {
+		opt60 = &dhcpv6.OptionGeneric{
+			OptionCode: dhcpv6.OptionBootfileParam,
+			OptionData: []byte(params),
+		}
+	}
+	log.Printf("loaded NBP plugin for DHCPv6.")
+	return nbpHandler6, nil
+}
+
+func setupNBP4(args ...string) (handler.Handler4, error) {
+	u, err := parseArgs(args...)
+	if err != nil {
+		return nil, err
+	}
+	otsn := dhcpv4.OptTFTPServerName(u.Host)
+	opt66 = &otsn
+	obfn := dhcpv4.OptBootFileName(u.Path)
+	opt67 = &obfn
+	log.Printf("loaded NBP plugin for DHCPv4.")
+	return nbpHandler4, nil
+}
+
+func nbpHandler6(req, resp dhcpv6.DHCPv6) (dhcpv6.DHCPv6, bool) {
+	if opt59 == nil {
+		// nothing to do
+		return resp, true
+	}
+	decap, err := req.GetInnerMessage()
+	if err != nil {
+		log.Errorf("Could not decapsulate request: %v", err)
+		// drop the request, this is probably a critical error in the packet.
+		return nil, true
+	}
+	if oro := decap.GetOption(dhcpv6.OptionORO); len(oro) > 0 {
+		for _, code := range oro[0].(*dhcpv6.OptRequestedOption).RequestedOptions() {
+			if code == dhcpv6.OptionBootfileURL {
+				// bootfile URL is requested
+				resp.AddOption(opt59)
+			} else if code == dhcpv6.OptionBootfileParam {
+				// optionally add opt60, bootfile params, if requested
+				if opt60 != nil {
+					resp.AddOption(opt60)
+				}
+			}
+		}
+	}
+	log.Debugf("Added NBP %s to request", opt59)
+	return resp, true
+}
+
+func nbpHandler4(req, resp *dhcpv4.DHCPv4) (*dhcpv4.DHCPv4, bool) {
+	if opt66 == nil || opt67 == nil {
+		// nothing to do
+		return resp, true
+	}
+	if req.IsOptionRequested(dhcpv4.OptionTFTPServerName) {
+		resp.Options.Update(*opt66)
+	}
+	if req.IsOptionRequested(dhcpv4.OptionBootfileName) {
+		resp.Options.Update(*opt67)
+	}
+	log.Debugf("Added NBP %s / %s to request", opt66, opt67)
+	return resp, true
+}