Allow announcing extra routes through DHCPv4

.github/workflows/tests.yml

@@ -38,6 +38,8 @@ jobs:
       - id: ShellCheck
         name: Differential ShellCheck
         uses: redhat-plumbers-in-action/differential-shellcheck@v5
+        env:
+          SHELLCHECK_OPTS: --shell sh
         with:
           token: ${{ secrets.GITHUB_TOKEN }}
         if: github.event_name == 'pull_request' && matrix.go == 'stable'

cmd/incusd/main_forknet.go

@@ -391,6 +391,21 @@ func (c *cmdForknet) RunDHCP(cmd *cobra.Command, args []string) error {
 		return nil
 	}
 
+	for _, staticRoute := range lease.Offer.ClasslessStaticRoute() {
+		route := &ip.Route{
+			DevName: iface,
+			Route:   staticRoute.Dest.String(),
+			Via:     staticRoute.Router.String(),
+			Family:  ip.FamilyV4,
+		}
+
+		err = route.Add()
+		if err != nil {
+			fmt.Fprintf(os.Stderr, "Giving up on DHCP, couldn't add classless static route to %q: %v\n", iface, err)
+			return nil
+		}
+	}
+
 	// Create PID file.
 	err = os.WriteFile(filepath.Join(args[0], "dhcp.pid"), []byte(fmt.Sprintf("%d", os.Getpid())), 0644)
 	if err != nil {

doc/.wordlist.txt

@@ -65,6 +65,7 @@ Diátaxis
 Diffie
 Distrobuilder
 DNS
+dnsmasq
 DNSSEC
 DoS
 DRM

doc/api-extensions.md

@@ -2717,3 +2717,7 @@ Adds support for `DNS-01` challenge to the Incus ACME support for certificate ge
 ## `security_iommu`
 Introduce a new `security.iommu` configuration key to control whether to
 enable IOMMU emulation. This is done through `virtio_iommu` on Linux and the emulated Intel IOMMU on Windows.
+
+## `network_ipv4_dhcp_routes`
+Introduces a new `ipv4.dhcp.routes` configuration option on bridged and OVN networks.
+This allows specifying pairs of CIDR networks and gateway address to be announced by the DHCP server.

doc/reference/network_bridge.md

@@ -75,6 +75,7 @@ Key                                  | Type      | Condition             | Defau
 `ipv4.dhcp.expiry`                   | string    | IPv4 DHCP             | `1h`                      | When to expire DHCP leases
 `ipv4.dhcp.gateway`                  | string    | IPv4 DHCP             | IPv4 address              | Address of the gateway for the subnet
 `ipv4.dhcp.ranges`                   | string    | IPv4 DHCP             | all addresses             | Comma-separated list of IP ranges to use for DHCP (FIRST-LAST format)
+`ipv4.dhcp.routes`                   | string    | IPv4 DHCP             | -                         | Static routes to provide via DHCP option 121, as a comma-separated list of alternating subnets (CIDR) and gateway addresses (same syntax as dnsmasq)
 `ipv4.firewall`                      | bool      | IPv4 address          | `true`                    | Whether to generate filtering firewall rules for this network
 `ipv4.nat`                           | bool      | IPv4 address          | `false` (initial value on creation if `ipv4.address` is set to `auto`: `true`) | Whether to NAT
 `ipv4.nat.address`                   | string    | IPv4 address          | -                         | The source address used for outbound traffic from the bridge

doc/reference/network_ovn.md

@@ -52,6 +52,7 @@ Key                                  | Type      | Condition             | Defau
 `dns.zone.reverse.ipv6`              | string    | -                     | -                         | DNS zone name for IPv6 reverse DNS records
 `ipv4.address`                       | string    | standard mode         | - (initial value on creation: `auto`) | IPv4 address for the bridge (use `none` to turn off IPv4 or `auto` to generate a new random unused subnet) (CIDR)
 `ipv4.dhcp`                          | bool      | IPv4 address          | `true`                    | Whether to allocate addresses using DHCP
+`ipv4.dhcp.routes`                   | string    | IPv4 DHCP             | -                         | Static routes to provide via DHCP option 121, as a comma-separated list of alternating subnets (CIDR) and gateway addresses (same syntax as dnsmasq and OVN)
 `ipv4.l3only`                        | bool      | IPv4 address          | `false`                   | Whether to enable layer 3 only mode.
 `ipv4.nat`                           | bool      | IPv4 address          | `false` (initial value on creation if `ipv4.address` is set to `auto`: `true`) | Whether to NAT
 `ipv4.nat.address`                   | string    | IPv4 address          | -                         | The source address used for outbound traffic from the network (requires uplink `ovn.ingress_mode=routed`)

internal/server/network/driver_bridge.go

@@ -183,6 +183,7 @@ func (n *bridge) Validate(config map[string]string) error {
 		"ipv4.dhcp.gateway": validate.Optional(validate.IsNetworkAddressV4),
 		"ipv4.dhcp.expiry":  validate.IsAny,
 		"ipv4.dhcp.ranges":  validate.Optional(validate.IsListOf(validate.IsNetworkRangeV4)),
+		"ipv4.dhcp.routes":  validate.Optional(validate.IsDHCPRouteList),
 		"ipv4.routes":       validate.Optional(validate.IsListOf(validate.IsNetworkV4)),
 		"ipv4.routing":      validate.Optional(validate.IsBool),
 		"ipv4.ovn.ranges":   validate.Optional(validate.IsListOf(validate.IsNetworkRangeV4)),
@@ -928,6 +929,10 @@ func (n *bridge) setup(oldConfig map[string]string) error {
 				dnsmasqCmd = append(dnsmasqCmd, fmt.Sprintf("--dhcp-option-force=119,%s", strings.Trim(dnsSearch, " ")))
 			}
 
+			if n.config["ipv4.dhcp.routes"] != "" {
+				dnsmasqCmd = append(dnsmasqCmd, fmt.Sprintf("--dhcp-option-force=121,%s", strings.Replace(n.config["ipv4.dhcp.routes"], " ", "", -1)))
+			}
+
 			expiry := "1h"
 			if n.config["ipv4.dhcp.expiry"] != "" {
 				expiry = n.config["ipv4.dhcp.expiry"]

internal/server/network/driver_ovn.go

@@ -394,6 +394,7 @@ func (n *ovn) Validate(config map[string]string) error {
 		}),
 		"ipv4.dhcp":        validate.Optional(validate.IsBool),
 		"ipv4.dhcp.ranges": validate.Optional(validate.IsListOf(validate.IsNetworkRangeV4)),
+		"ipv4.dhcp.routes": validate.Optional(validate.IsDHCPRouteList),
 		"ipv6.address": validate.Optional(func(value string) error {
 			if validate.IsOneOf("none", "auto")(value) == nil {
 				return nil
@@ -2656,6 +2657,7 @@ func (n *ovn) setup(update bool) error {
 			MTU:           bridgeMTU,
 			Netmask:       dhcpV4Netmask,
 			DNSSearchList: n.getDNSSearchList(),
+			StaticRoutes:  n.config["ipv4.dhcp.routes"],
 		}
 
 		if uplinkNet != nil {

internal/server/network/ovn/ovn_nb_actions.go

@@ -108,6 +108,7 @@ type OVNDHCPv4Opts struct {
 	MTU                uint32
 	Netmask            string
 	DNSSearchList      []string
+	StaticRoutes       string
 }
 
 // OVNDHCPv6Opts IPv6 DHCP option set that can be created (and then applied to a switch port by resulting ID).
@@ -1287,6 +1288,12 @@ func (o *NB) UpdateLogicalSwitchDHCPv4Options(ctx context.Context, switchName OV
 		dhcpOption.Options["netmask"] = opts.Netmask
 	}
 
+	if opts.StaticRoutes != "" {
+		dhcpOption.Options["classless_static_route"] = fmt.Sprintf("{%s}", opts.StaticRoutes)
+	} else {
+		delete(dhcpOption.Options, "classless_static_route")
+	}
+
 	// Prepare the changes.
 	operations := []ovsdb.Operation{}
 	if dhcpOption.UUID == "" {

internal/version/api.go

@@ -466,6 +466,7 @@ var APIExtensions = []string{
 	"api_filtering_extended",
 	"acme_dns01",
 	"security_iommu",
+	"network_ipv4_dhcp_routes",
 }
 
 // APIExtensionsCount returns the number of available API extensions.

shared/validate/validate.go

@@ -512,6 +512,30 @@ func IsNetworkPortRange(value string) error {
 	return nil
 }
 
+// IsDHCPRouteList validates a comma-separated list of alternating CIDR networks and IP addresses.
+func IsDHCPRouteList(value string) error {
+	parts := strings.Split(value, ",")
+	for i, s := range parts {
+		// routes are pairs of subnet and gateway
+		var err error
+		if i%2 == 0 { // subnet part
+			err = IsNetworkV4(s)
+		} else { // gateway part
+			err = IsNetworkAddressV4(s)
+		}
+
+		if err != nil {
+			return err
+		}
+	}
+
+	if len(parts)%2 != 0 { // uneven number of parts means the gateway of the last route is missing
+		return fmt.Errorf("missing gateway for route %v", parts[len(parts)-1])
+	}
+
+	return nil
+}
+
 // IsURLSegmentSafe validates whether value can be used in a URL segment.
 func IsURLSegmentSafe(value string) error {
 	for _, char := range []string{"/", "?", "&", "+"} {

test/main.sh

@@ -318,6 +318,7 @@ if [ "${1:-"all"}" != "cluster" ]; then
     run_test test_server_config "server configuration"
     run_test test_filemanip "file manipulations"
     run_test test_network "network management"
+    run_test test_network_dhcp_routes "network dhcp routes"
     run_test test_network_acl "network ACL management"
     run_test test_network_forward "network address forwards"
     run_test test_network_zone "network DNS zones"

test/suites/network_dhcp_routes.sh

@@ -0,0 +1,60 @@
+test_network_dhcp_routes() {
+  ensure_import_testimage
+  ensure_has_localhost_remote "${INCUS_ADDR}"
+
+  # bridge network
+  incus network create inct$$
+  incus network set inct$$ ipv4.address 10.13.37.1/24
+  incus network set inct$$ ipv4.dhcp.routes 1.2.0.0/16,10.13.37.5,2.3.0.0/16,10.13.37.7
+
+  incus launch testimage nettest -n inct$$
+
+  cat > "${TEST_DIR}"/udhcpc.sh <<EOL
+#!/bin/sh
+[ "\$1" = "bound" ] && echo "STATICROUTES: \$staticroutes"
+EOL
+
+  incus file push "${TEST_DIR}/udhcpc.sh" nettest/udhcpc.sh
+  incus exec nettest -- chmod a+rx /udhcpc.sh
+
+  staticroutes_output=$(incus exec nettest -- udhcpc -s /udhcpc.sh 2>/dev/null | grep STATICROUTES)
+
+  echo "$staticroutes_output" | grep -q "1.2.0.0/16 10.13.37.5"
+  echo "$staticroutes_output" | grep -q "2.3.0.0/16 10.13.37.7"
+
+  incus delete nettest -f
+
+  if [ -n "${INCUS_OFFLINE:-}" ]; then
+    echo "==> SKIP: Skipping OCI tests as running offline"
+  else
+    ensure_has_localhost_remote "${INCUS_ADDR}"
+
+    incus remote add docker https://docker.io --protocol=oci
+    incus launch docker:alpine nettest --network=inct$$
+
+    incus exec nettest -- ip route list | grep -q "1.2.0.0/16 via 10.13.37.5"
+    incus exec nettest -- ip route list | grep -q "2.3.0.0/16 via 10.13.37.7"
+
+    incus delete -f nettest
+    incus remote remove docker
+  fi
+
+  incus network delete inct$$
+
+
+  # ovn network
+  if incus network create inct$$ -t ovn network=none; then
+    incus network set inct$$ ipv4.address 10.13.37.1/24
+    incus network set inct$$ ipv4.dhcp.routes 1.2.0.0/16,10.13.37.5,2.3.0.0/16,10.13.37.7
+
+    incus launch testimage nettest -n inct$$
+
+    incus exec nettest -- ip route list | grep -q "1.2.0.0/16 via 10.13.37.5"
+    incus exec nettest -- ip route list | grep -q "2.3.0.0/16 via 10.13.37.7"
+
+    incus delete nettest -f
+    incus network delete inct$$
+  else
+    echo "==> SKIP: Skipping OVN tests"
+  fi
+}