osbase/net/dhcp4c: move package out of metropolis
Move the dhcp4c package from metropolis/node/core/network/dhcp4c to
osbase/net/dhcp4c. The package is not specific to metropolis, and is
also used by nanoswitch and cloud/agent.
Change-Id: I508261c93c623d5b7a33a2089da11625b7a3abd0
Reviewed-on: https://review.monogon.dev/c/monogon/+/4565
Tested-by: Jenkins CI
Reviewed-by: Tim Windelschmidt <tim@monogon.tech>
diff --git a/osbase/net/dhcp4c/callback/BUILD.bazel b/osbase/net/dhcp4c/callback/BUILD.bazel
new file mode 100644
index 0000000..a8780fc
--- /dev/null
+++ b/osbase/net/dhcp4c/callback/BUILD.bazel
@@ -0,0 +1,33 @@
+load("@io_bazel_rules_go//go:def.bzl", "go_library", "go_test")
+load("//osbase/test/ktest:ktest.bzl", "k_test")
+
+go_library(
+ name = "callback",
+ srcs = ["callback.go"],
+ importpath = "source.monogon.dev/osbase/net/dhcp4c/callback",
+ visibility = ["//visibility:public"],
+ deps = [
+ "//osbase/net/dhcp4c",
+ "@com_github_insomniacslk_dhcp//dhcpv4",
+ "@com_github_vishvananda_netlink//:netlink",
+ "@org_golang_x_sys//unix",
+ ],
+)
+
+go_test(
+ name = "callback_test",
+ srcs = ["callback_test.go"],
+ embed = [":callback"],
+ deps = [
+ "//osbase/net/dhcp4c",
+ "@com_github_google_go_cmp//cmp",
+ "@com_github_insomniacslk_dhcp//dhcpv4",
+ "@com_github_vishvananda_netlink//:netlink",
+ "@org_golang_x_sys//unix",
+ ],
+)
+
+k_test(
+ name = "ktest",
+ tester = ":callback_test",
+)
diff --git a/osbase/net/dhcp4c/callback/callback.go b/osbase/net/dhcp4c/callback/callback.go
new file mode 100644
index 0000000..dc3088b
--- /dev/null
+++ b/osbase/net/dhcp4c/callback/callback.go
@@ -0,0 +1,159 @@
+// Copyright The Monogon Project Authors.
+// SPDX-License-Identifier: Apache-2.0
+
+// Package callback contains minimal callbacks for configuring the kernel with
+// options received over DHCP.
+//
+// These directly configure the relevant kernel subsytems and need to own
+// certain parts of them as documented on a per- callback basis to make sure
+// that they can recover from restarts and crashes of the DHCP client.
+// The callbacks in here are not suitable for use in advanced network scenarios
+// like running multiple DHCP clients per interface via ClientIdentifier or
+// when running an external FIB manager. In these cases it's advised to extract
+// the necessary information from the lease in your own callback and
+// communicate it directly to the responsible entity.
+package callback
+
+import (
+ "fmt"
+ "math"
+ "net"
+ "os"
+ "time"
+
+ "github.com/insomniacslk/dhcp/dhcpv4"
+ "github.com/vishvananda/netlink"
+ "golang.org/x/sys/unix"
+
+ "source.monogon.dev/osbase/net/dhcp4c"
+)
+
+// Compose can be used to chain multiple callbacks
+func Compose(callbacks ...dhcp4c.LeaseCallback) dhcp4c.LeaseCallback {
+ return func(lease *dhcp4c.Lease) error {
+ for _, cb := range callbacks {
+ if err := cb(lease); err != nil {
+ return err
+ }
+ }
+ return nil
+ }
+}
+
+func isIPNetEqual(a, b *net.IPNet) bool {
+ if a == b {
+ return true
+ }
+ if a == nil || b == nil {
+ return false
+ }
+ aOnes, aBits := a.Mask.Size()
+ bOnes, bBits := b.Mask.Size()
+ return a.IP.Equal(b.IP) && aOnes == bOnes && aBits == bBits
+}
+
+// ManageIP sets up and tears down the assigned IP address. It takes exclusive
+// ownership of all IPv4 addresses on the given interface which do not have
+// IFA_F_PERMANENT set, so it's not possible to run multiple dynamic addressing
+// clients on a single interface.
+func ManageIP(iface netlink.Link) dhcp4c.LeaseCallback {
+ return func(lease *dhcp4c.Lease) error {
+ newNet := lease.IPNet()
+
+ addrs, err := netlink.AddrList(iface, netlink.FAMILY_V4)
+ if err != nil {
+ return fmt.Errorf("netlink failed to list addresses: %w", err)
+ }
+
+ for _, addr := range addrs {
+ if addr.Flags&unix.IFA_F_PERMANENT == 0 {
+ // Linux identifies addreses by IP, mask and peer (see
+ // net/ipv4/devinet.find_matching_ifa in Linux 5.10).
+ // So don't touch addresses which match on these properties as
+ // AddrReplace will atomically reconfigure them anyways without
+ // interrupting things.
+ if isIPNetEqual(addr.IPNet, newNet) && addr.Peer == nil && lease != nil {
+ continue
+ }
+
+ if err := netlink.AddrDel(iface, &addr); !os.IsNotExist(err) && err != nil {
+ return fmt.Errorf("failed to delete address: %w", err)
+ }
+ }
+ }
+
+ if lease != nil {
+ remainingLifetimeSecs := int(math.Ceil(time.Until(lease.ExpiresAt).Seconds()))
+ newBroadcastIP := dhcpv4.GetIP(dhcpv4.OptionBroadcastAddress, lease.Options)
+ if err := netlink.AddrReplace(iface, &netlink.Addr{
+ IPNet: newNet,
+ ValidLft: remainingLifetimeSecs,
+ PreferedLft: remainingLifetimeSecs,
+ Broadcast: newBroadcastIP,
+ }); err != nil {
+ return fmt.Errorf("failed to update address: %w", err)
+ }
+ }
+ return nil
+ }
+}
+
+// ManageRoutes installs and removes routes according to the current DHCP lease,
+// including the default route (if any).
+// It takes ownership of all RTPROTO_DHCP routes on the given interface, so it's
+// not possible to run multiple DHCP clients on the given interface.
+func ManageRoutes(iface netlink.Link) dhcp4c.LeaseCallback {
+ return func(lease *dhcp4c.Lease) error {
+ newRoutes := lease.Routes()
+
+ dhcpRoutes, err := netlink.RouteListFiltered(netlink.FAMILY_V4, &netlink.Route{
+ Protocol: unix.RTPROT_DHCP,
+ LinkIndex: iface.Attrs().Index,
+ }, netlink.RT_FILTER_OIF|netlink.RT_FILTER_PROTOCOL)
+ if err != nil {
+ return fmt.Errorf("netlink failed to list routes: %w", err)
+ }
+ for _, route := range dhcpRoutes {
+ // Don't remove routes which can be atomically replaced by
+ // RouteReplace to prevent potential traffic disruptions.
+ //
+ // This is O(n^2) but the number of routes is bounded by the size
+ // of a DHCP packet (around 100 routes). Sorting both would be
+ // be marginally faster for large amounts of routes only and in 99%
+ // of cases it's going to be <5 routes.
+ var found bool
+ for _, newRoute := range newRoutes {
+ if isIPNetEqual(newRoute.Dest, route.Dst) {
+ found = true
+ break
+ }
+ }
+ if !found {
+ err := netlink.RouteDel(&route)
+ if !os.IsNotExist(err) && err != nil {
+ return fmt.Errorf("failed to delete DHCP route: %w", err)
+ }
+ }
+ }
+
+ for _, route := range newRoutes {
+ newRoute := netlink.Route{
+ Protocol: unix.RTPROT_DHCP,
+ Dst: route.Dest,
+ Gw: route.Router,
+ Src: lease.AssignedIP,
+ LinkIndex: iface.Attrs().Index,
+ Scope: netlink.SCOPE_UNIVERSE,
+ }
+ // Routes with a non-L3 gateway are link-scoped
+ if route.Router.IsUnspecified() {
+ newRoute.Scope = netlink.SCOPE_LINK
+ }
+ err := netlink.RouteReplace(&newRoute)
+ if err != nil {
+ return fmt.Errorf("failed to add %s: %w", route, err)
+ }
+ }
+ return nil
+ }
+}
diff --git a/osbase/net/dhcp4c/callback/callback_test.go b/osbase/net/dhcp4c/callback/callback_test.go
new file mode 100644
index 0000000..db616bb
--- /dev/null
+++ b/osbase/net/dhcp4c/callback/callback_test.go
@@ -0,0 +1,355 @@
+// Copyright The Monogon Project Authors.
+// SPDX-License-Identifier: Apache-2.0
+
+package callback
+
+import (
+ "fmt"
+ "math"
+ "net"
+ "os"
+ "testing"
+ "time"
+
+ "github.com/google/go-cmp/cmp"
+ "github.com/insomniacslk/dhcp/dhcpv4"
+ "github.com/vishvananda/netlink"
+ "golang.org/x/sys/unix"
+
+ "source.monogon.dev/osbase/net/dhcp4c"
+)
+
+func trivialLeaseFromNet(ipnet net.IPNet) *dhcp4c.Lease {
+ opts := make(dhcpv4.Options)
+ opts.Update(dhcpv4.OptSubnetMask(ipnet.Mask))
+ return &dhcp4c.Lease{
+ AssignedIP: ipnet.IP,
+ ExpiresAt: time.Now().Add(1 * time.Second),
+ Options: opts,
+ }
+}
+
+var (
+ testNet1 = net.IPNet{IP: net.IP{10, 0, 1, 2}, Mask: net.CIDRMask(24, 32)}
+ testNet1Broadcast = net.IP{10, 0, 1, 255}
+ testNet1Router = net.IP{10, 0, 1, 1}
+ testNet2 = net.IPNet{IP: net.IP{10, 0, 2, 2}, Mask: net.CIDRMask(24, 32)}
+ testNet2Broadcast = net.IP{10, 0, 2, 255}
+ testNet2Router = net.IP{10, 0, 2, 1}
+ mainRoutingTable = 254 // Linux automatically puts all routes into this table unless specified
+)
+
+func TestAssignedIPCallback(t *testing.T) {
+ if os.Getenv("IN_KTEST") != "true" {
+ t.Skip("Not in ktest")
+ }
+
+ var tests = []struct {
+ name string
+ initialAddrs []netlink.Addr
+ newLease *dhcp4c.Lease
+ expectedAddrs []netlink.Addr
+ }{
+ // Lifetimes are necessary, otherwise the Kernel sets the
+ // IFA_F_PERMANENT flag behind our back.
+ {
+ name: "RemoveOldIPs",
+ initialAddrs: []netlink.Addr{{IPNet: &testNet1, ValidLft: 60}, {IPNet: &testNet2, ValidLft: 60}},
+ newLease: nil,
+ expectedAddrs: nil,
+ },
+ {
+ name: "IgnoresPermanentIPs",
+ initialAddrs: []netlink.Addr{{IPNet: &testNet1, Flags: unix.IFA_F_PERMANENT}, {IPNet: &testNet2, ValidLft: 60}},
+ newLease: trivialLeaseFromNet(testNet2),
+ expectedAddrs: []netlink.Addr{
+ {IPNet: &testNet1, Flags: unix.IFA_F_PERMANENT, ValidLft: math.MaxUint32, PreferedLft: math.MaxUint32, Broadcast: testNet1Broadcast},
+ {IPNet: &testNet2, ValidLft: 1, PreferedLft: 1, Broadcast: testNet2Broadcast},
+ },
+ },
+ {
+ name: "AssignsNewIP",
+ initialAddrs: []netlink.Addr{},
+ newLease: trivialLeaseFromNet(testNet2),
+ expectedAddrs: []netlink.Addr{
+ {IPNet: &testNet2, ValidLft: 1, PreferedLft: 1, Broadcast: testNet2Broadcast},
+ },
+ },
+ {
+ name: "UpdatesIP",
+ initialAddrs: []netlink.Addr{},
+ newLease: trivialLeaseFromNet(testNet1),
+ expectedAddrs: []netlink.Addr{
+ {IPNet: &testNet1, ValidLft: 1, PreferedLft: 1, Broadcast: testNet1Broadcast},
+ },
+ },
+ {
+ name: "RemovesIPOnRelease",
+ initialAddrs: []netlink.Addr{{IPNet: &testNet1, ValidLft: 60, PreferedLft: 60}},
+ newLease: nil,
+ expectedAddrs: nil,
+ },
+ }
+ for i, test := range tests {
+ t.Run(test.name, func(t *testing.T) {
+ testLink := &netlink.Dummy{
+ LinkAttrs: netlink.LinkAttrs{
+ Name: fmt.Sprintf("aipcb-test-%d", i),
+ Flags: unix.IFF_UP,
+ },
+ }
+ if err := netlink.LinkAdd(testLink); err != nil {
+ t.Fatalf("test cannot set up network interface: %v", err)
+ }
+ defer netlink.LinkDel(testLink)
+ for _, addr := range test.initialAddrs {
+ if err := netlink.AddrAdd(testLink, &addr); err != nil {
+ t.Fatalf("test cannot set up initial addrs: %v", err)
+ }
+ }
+ // Associate dynamically-generated interface name for later comparison
+ for i := range test.expectedAddrs {
+ test.expectedAddrs[i].Label = testLink.Name
+ test.expectedAddrs[i].LinkIndex = testLink.Index
+ }
+ cb := ManageIP(testLink)
+ if err := cb(test.newLease); err != nil {
+ t.Fatalf("callback returned an error: %v", err)
+ }
+ addrs, err := netlink.AddrList(testLink, netlink.FAMILY_V4)
+ if err != nil {
+ t.Fatalf("test cannot read back addrs from interface: %v", err)
+ }
+ if diff := cmp.Diff(test.expectedAddrs, addrs); diff != "" {
+ t.Errorf("Wrong IPs on interface (-want +got):\n%s", diff)
+ }
+ })
+ }
+}
+
+func leaseAddRouter(lease *dhcp4c.Lease, router net.IP) *dhcp4c.Lease {
+ lease.Options.Update(dhcpv4.OptRouter(router))
+ return lease
+}
+
+func leaseAddClasslessRoutes(lease *dhcp4c.Lease, routes ...*dhcpv4.Route) *dhcp4c.Lease {
+ lease.Options.Update(dhcpv4.OptClasslessStaticRoute(routes...))
+ return lease
+}
+
+func mustParseCIDR(cidr string) *net.IPNet {
+ _, n, err := net.ParseCIDR(cidr)
+ if err != nil {
+ panic(err)
+ }
+ // Equality checks don't know about net.IP's canonicalization rules.
+ if n.IP.To4() != nil {
+ n.IP = n.IP.To4()
+ }
+ return n
+}
+
+func TestDefaultRouteCallback(t *testing.T) {
+ if os.Getenv("IN_KTEST") != "true" {
+ t.Skip("Not in ktest")
+ }
+ // testRoute is only used as a route destination and not configured on any
+ // interface.
+ testRoute := net.IPNet{IP: net.IP{10, 0, 3, 0}, Mask: net.CIDRMask(24, 32)}
+
+ // A test interface is set up for each test and assigned testNet1 and
+ // testNet2 so that testNet1Router and testNet2Router are valid gateways
+ // for routes in this environment. A LinkIndex of -1 is replaced by the
+ // correct link index for this test interface at runtime for both
+ // initialRoutes and expectedRoutes.
+ var tests = []struct {
+ name string
+ initialRoutes []netlink.Route
+ newLease *dhcp4c.Lease
+ expectedRoutes []netlink.Route
+ }{
+ {
+ name: "AddsDefaultRoute",
+ initialRoutes: []netlink.Route{},
+ newLease: leaseAddRouter(trivialLeaseFromNet(testNet1), testNet1Router),
+ expectedRoutes: []netlink.Route{{
+ Protocol: unix.RTPROT_DHCP,
+ Dst: mustParseCIDR("0.0.0.0/0"),
+ Family: unix.AF_INET,
+ Gw: testNet1Router,
+ Src: testNet1.IP,
+ Table: mainRoutingTable,
+ LinkIndex: -1, // Filled in dynamically with test interface
+ Type: unix.RTN_UNICAST,
+ }},
+ },
+ {
+ name: "IgnoresLeasesWithoutRouter",
+ initialRoutes: []netlink.Route{},
+ newLease: trivialLeaseFromNet(testNet1),
+ expectedRoutes: nil,
+ },
+ {
+ name: "RemovesUnrelatedOldRoutes",
+ initialRoutes: []netlink.Route{{
+ Dst: &testRoute,
+ Family: unix.AF_INET,
+ LinkIndex: -1, // Filled in dynamically with test interface
+ Protocol: unix.RTPROT_DHCP,
+ Gw: testNet2Router,
+ Scope: netlink.SCOPE_UNIVERSE,
+ }},
+ newLease: nil,
+ expectedRoutes: nil,
+ },
+ {
+ name: "IgnoresNonDHCPRoutes",
+ initialRoutes: []netlink.Route{{
+ Dst: &testRoute,
+ Family: unix.AF_INET,
+ LinkIndex: -1, // Filled in dynamically with test interface
+ Protocol: unix.RTPROT_BIRD,
+ Gw: testNet2Router,
+ }},
+ newLease: nil,
+ expectedRoutes: []netlink.Route{{
+ Protocol: unix.RTPROT_BIRD,
+ Dst: &testRoute,
+ Family: unix.AF_INET,
+ Gw: testNet2Router,
+ Table: mainRoutingTable,
+ LinkIndex: -1, // Filled in dynamically with test interface
+ Type: unix.RTN_UNICAST,
+ }},
+ },
+ {
+ name: "RemovesRoute",
+ initialRoutes: []netlink.Route{{
+ Dst: nil,
+ Family: unix.AF_INET,
+ LinkIndex: -1, // Filled in dynamically with test interface
+ Protocol: unix.RTPROT_DHCP,
+ Gw: testNet2Router,
+ }},
+ newLease: nil,
+ expectedRoutes: nil,
+ },
+ {
+ name: "UpdatesRoute",
+ initialRoutes: []netlink.Route{{
+ Dst: nil,
+ Family: unix.AF_INET,
+ LinkIndex: -1, // Filled in dynamically with test interface
+ Protocol: unix.RTPROT_DHCP,
+ Src: testNet1.IP,
+ Gw: testNet1Router,
+ }},
+ newLease: leaseAddRouter(trivialLeaseFromNet(testNet2), testNet2Router),
+ expectedRoutes: []netlink.Route{{
+ Protocol: unix.RTPROT_DHCP,
+ Dst: mustParseCIDR("0.0.0.0/0"),
+ Family: unix.AF_INET,
+ Gw: testNet2Router,
+ Src: testNet2.IP,
+ Table: mainRoutingTable,
+ LinkIndex: -1, // Filled in dynamically with test interface
+ Type: unix.RTN_UNICAST,
+ }},
+ },
+ {
+ name: "AddsClasslessStaticRoutes",
+ initialRoutes: []netlink.Route{},
+ newLease: leaseAddClasslessRoutes(
+ // Router should be ignored
+ leaseAddRouter(trivialLeaseFromNet(testNet1), testNet1Router),
+ // P2P/foreign gateway route
+ &dhcpv4.Route{Dest: mustParseCIDR("192.168.42.1/32"), Router: net.IPv4zero},
+ // Standard route over foreign gateway set up by previous route
+ &dhcpv4.Route{Dest: mustParseCIDR("0.0.0.0/0"), Router: net.IPv4(192, 168, 42, 1)},
+ ),
+ expectedRoutes: []netlink.Route{{
+ Protocol: unix.RTPROT_DHCP,
+ Dst: mustParseCIDR("0.0.0.0/0"),
+ Family: unix.AF_INET,
+ Gw: net.IPv4(192, 168, 42, 1).To4(), // Equal() doesn't know about canonicalization
+ Src: testNet1.IP,
+ Table: mainRoutingTable,
+ LinkIndex: -1, // Filled in dynamically with test interface
+ Type: unix.RTN_UNICAST,
+ }, {
+ Protocol: unix.RTPROT_DHCP,
+ Dst: mustParseCIDR("192.168.42.1/32"),
+ Family: unix.AF_INET,
+ Gw: nil,
+ Src: testNet1.IP,
+ Table: mainRoutingTable,
+ LinkIndex: -1, // Filled in dynamically with test interface
+ Type: unix.RTN_UNICAST,
+ Scope: unix.RT_SCOPE_LINK,
+ }},
+ },
+ }
+ for i, test := range tests {
+ t.Run(test.name, func(t *testing.T) {
+ testLink := &netlink.Dummy{
+ LinkAttrs: netlink.LinkAttrs{
+ Name: fmt.Sprintf("drcb-test-%d", i),
+ Flags: unix.IFF_UP,
+ },
+ }
+ if err := netlink.LinkAdd(testLink); err != nil {
+ t.Fatalf("test cannot set up network interface: %v", err)
+ }
+ defer func() { // Clean up after each test
+ routes, err := netlink.RouteListFiltered(netlink.FAMILY_V4, &netlink.Route{}, 0)
+ if err == nil {
+ for _, route := range routes {
+ netlink.RouteDel(&route)
+ }
+ }
+ }()
+ defer netlink.LinkDel(testLink)
+ if err := netlink.AddrAdd(testLink, &netlink.Addr{
+ IPNet: &testNet1,
+ }); err != nil {
+ t.Fatalf("test cannot set up test addrs: %v", err)
+ }
+ if err := netlink.AddrAdd(testLink, &netlink.Addr{
+ IPNet: &testNet2,
+ }); err != nil {
+ t.Fatalf("test cannot set up test addrs: %v", err)
+ }
+ for _, route := range test.initialRoutes {
+ if route.LinkIndex == -1 {
+ route.LinkIndex = testLink.Index
+ }
+ if err := netlink.RouteAdd(&route); err != nil {
+ t.Fatalf("test cannot set up initial routes: %v", err)
+ }
+ }
+ for i := range test.expectedRoutes {
+ if test.expectedRoutes[i].LinkIndex == -1 {
+ test.expectedRoutes[i].LinkIndex = testLink.Index
+ }
+ }
+
+ cb := ManageRoutes(testLink)
+ if err := cb(test.newLease); err != nil {
+ t.Fatalf("callback returned an error: %v", err)
+ }
+ routes, err := netlink.RouteListFiltered(netlink.FAMILY_V4, &netlink.Route{}, 0)
+ if err != nil {
+ t.Fatalf("test cannot read back routes: %v", err)
+ }
+ var notKernelRoutes []netlink.Route
+ for _, route := range routes {
+ if route.Protocol != unix.RTPROT_KERNEL { // Filter kernel-managed routes
+ notKernelRoutes = append(notKernelRoutes, route)
+ }
+ }
+ if diff := cmp.Diff(test.expectedRoutes, notKernelRoutes); diff != "" {
+ t.Errorf("Expected route mismatch (-want +got):\n%s", diff)
+ }
+ })
+ }
+}