Introduce VSOCK link type

This address family is used in communication between virtual machines
and their hosts. Advantages include that no virtual ethernet adapter
and their respective address configuration and routing need to be
setup. Rather, with this new link type, only a single yggdrasil
interface can exist inside of the virtual machine.

It can also be used inside of containers. There, the advantage over
existing link types like unix sockets include, that no mount point
need to be shared with the host and container. This provides more
isolation.

More information:

https://man7.org/linux/man-pages/man7/vsock.7.html

https://gist.github.com/nrdmn/7971be650919b112343b1cb2757a3fe6

CHANGELOG.md

@@ -26,6 +26,13 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 - in case of vulnerabilities.
 -->
 
+## [0.5.xx] - 2025-xx-xx
+
+### Added
+
+* VSOCK support for peerings, by using the new `vsock://` scheme in `Listen` and `Peers`.
+ * Use e.g. `vsock://local:1234`.
+
 ## [0.5.12] - 2024-12-18
 
 * Go 1.22 is now required to build Yggdrasil

go.mod

@@ -11,6 +11,7 @@ require (
 	github.com/hashicorp/go-syslog v1.0.0
 	github.com/hjson/hjson-go/v4 v4.4.0
 	github.com/kardianos/minwinsvc v1.0.2
+	github.com/mdlayher/vsock v1.2.1
 	github.com/quic-go/quic-go v0.48.2
 	github.com/vishvananda/netlink v1.3.0
 	github.com/wlynxg/anet v0.0.5
@@ -29,6 +30,7 @@ require (
 	github.com/go-task/slim-sprig v0.0.0-20230315185526-52ccab3ef572 // indirect
 	github.com/google/pprof v0.0.0-20210407192527-94a9f03dee38 // indirect
 	github.com/mattn/go-colorable v0.1.13 // indirect
+	github.com/mdlayher/socket v0.4.1 // indirect
 	github.com/onsi/ginkgo/v2 v2.9.5 // indirect
 	github.com/rivo/uniseg v0.2.0 // indirect
 	go.uber.org/mock v0.5.0 // indirect

go.sum

@@ -50,6 +50,10 @@ github.com/mattn/go-isatty v0.0.20/go.mod h1:W+V8PltTTMOvKvAeJH7IuucS94S2C6jfK/D
 github.com/mattn/go-runewidth v0.0.9/go.mod h1:H031xJmbD/WCDINGzjvQ9THkh0rPKHF+m2gUSrubnMI=
 github.com/mattn/go-runewidth v0.0.16 h1:E5ScNMtiwvlvB5paMFdw9p4kSQzbXFikJ5SQO6TULQc=
 github.com/mattn/go-runewidth v0.0.16/go.mod h1:Jdepj2loyihRzMpdS35Xk/zdY8IAYHsh153qUoGf23w=
+github.com/mdlayher/socket v0.4.1 h1:eM9y2/jlbs1M615oshPQOHZzj6R6wMT7bX5NPiQvn2U=
+github.com/mdlayher/socket v0.4.1/go.mod h1:cAqeGjoufqdxWkD7DkpyS+wcefOtmu5OQ8KuoJGIReA=
+github.com/mdlayher/vsock v1.2.1 h1:pC1mTJTvjo1r9n9fbm7S1j04rCgCzhCOS5DY0zqHlnQ=
+github.com/mdlayher/vsock v1.2.1/go.mod h1:NRfCibel++DgeMD8z/hP+PPTjlNJsdPOmxcnENvE+SE=
 github.com/olekukonko/tablewriter v0.0.5 h1:P2Ga83D34wi1o9J6Wh1mRuqd4mF/x/lgBS7N7AbDhec=
 github.com/olekukonko/tablewriter v0.0.5/go.mod h1:hPp6KlRPjbx+hW8ykQs1w3UBbZlj6HuIJcUGPhkA7kY=
 github.com/onsi/ginkgo/v2 v2.9.5 h1:+6Hr4uxzP4XIUyAkg61dWBw8lb/gc4/X5luuxN/EC+Q=

src/core/link.go

@@ -40,6 +40,7 @@ type links struct {
 	quic  *linkQUIC  // QUIC interface support
 	ws    *linkWS    // WS interface support
 	wss   *linkWSS   // WSS interface support
+	vsock *linkVSOCK // VSOCK interface support
 	// _links can only be modified safely from within the links actor
 	_links     map[linkInfo]*link // *link is nil if connection in progress
 	_listeners map[*Listener]context.CancelFunc
@@ -96,6 +97,7 @@ func (l *links) init(c *Core) error {
 	l.quic = l.newLinkQUIC()
 	l.ws = l.newLinkWS()
 	l.wss = l.newLinkWSS()
+	l.vsock = l.newLinkVSOCK()
 	l._links = make(map[linkInfo]*link)
 	l._listeners = make(map[*Listener]context.CancelFunc)
 
@@ -444,6 +446,8 @@ func (l *links) listen(u *url.URL, sintf string, local bool) (*Listener, error)
 		protocol = l.ws
 	case "wss":
 		protocol = l.wss
+	case "vsock":
+		protocol = l.vsock
 	default:
 		ctxcancel()
 		return nil, ErrLinkUnrecognisedSchema
@@ -595,6 +599,8 @@ func (l *links) connect(ctx context.Context, u *url.URL, info linkInfo, options
 		dialer = l.ws
 	case "wss":
 		dialer = l.wss
+	case "vsock":
+		dialer = l.vsock
 	default:
 		return nil, ErrLinkUnrecognisedSchema
 	}

src/core/link_vsock.go

@@ -0,0 +1,69 @@
+package core
+
+import (
+	"context"
+	"fmt"
+	"net"
+	"net/url"
+	"strconv"
+	"strings"
+
+	"github.com/Arceliar/phony"
+	"github.com/mdlayher/vsock"
+)
+
+type linkVSOCK struct {
+	phony.Inbox
+	*links
+}
+
+func (l *links) newLinkVSOCK() *linkVSOCK {
+	lt := &linkVSOCK{
+		links: l,
+	}
+	return lt
+}
+
+func (l *linkVSOCK) dial(ctx context.Context, url *url.URL, info linkInfo, options linkOptions) (net.Conn, error) {
+	localPort, err := strconv.ParseUint(url.Port(), 10, 32)
+	if err != nil {
+		return nil, fmt.Errorf("no VSOCK port specified: %w", err)
+	}
+	contextID, err := urlParseContextID(url)
+	if err != nil {
+		return nil, fmt.Errorf("Unknown VSOCK host and cannot parse as numerical contextID: %w", err)
+	}
+	return vsock.Dial(contextID, uint32(localPort), nil)
+}
+
+func (l *linkVSOCK) listen(ctx context.Context, url *url.URL, _ string) (net.Listener, error) {
+	localPort, err := strconv.ParseUint(url.Port(), 10, 32)
+	if err != nil {
+		return nil, fmt.Errorf("no VSOCK port specified: %w", err)
+	}
+	contextID, err := urlParseContextID(url)
+	if err != nil {
+		return nil, fmt.Errorf("Unknown VSOCK host and cannot parse as numerical contextID: %w", err)
+	}
+	return vsock.ListenContextID(contextID, uint32(localPort), nil)
+}
+
+func urlParseContextID(u *url.URL) (uint32, error) {
+	var contextID uint32
+
+	switch strings.ToLower(u.Hostname()) {
+	case "hypervisor":
+		contextID = vsock.Hypervisor
+	case "local":
+		contextID = vsock.Local
+	case "host":
+		contextID = vsock.Host
+	default:
+		parsedHost, err := strconv.ParseUint(u.Hostname(), 10, 32)
+		if err != nil {
+			return 0, err
+		}
+		contextID = uint32(parsedHost)
+	}
+	return contextID, nil
+}