From ded50996be6d26cefa9053c0b4d34207584eecaa Mon Sep 17 00:00:00 2001
From: Simon Ruderich <simon@ruderich.org>
Date: Wed, 30 Apr 2025 10:14:40 +0200
Subject: [PATCH] config: "link": make net-name optional for unnumbered
 ptp-links

Helped-by: Luca <luca@daerich.com>
---
 README.adoc | 13 +++++++------
 config.go   | 28 ++++++++++++++++------------
 2 files changed, 23 insertions(+), 18 deletions(-)

diff --git a/README.adoc b/README.adoc
index 1ec8238..a3bc458 100644
--- a/README.adoc
+++ b/README.adoc
@@ -141,14 +141,15 @@ new interface "lo2".
 
 === Option "link"
 
-    "link" <node> <node> <net-name> ["l3"]
+    "link" <node> <node> <net-name>|"-" ["l3"]
 
 "link" creates links between nodes. The IP addresses are taken from the given
-network name. /31 is used for IPv4- and /127 for IPv6-prefixes. The MAC
-address is not static and allocated by the kernel. The link is named after the
-node "on the other side". Multiple links can be created between two nodes. In
-this case "_2", "_3", etc. is appended to the interface name. By default veth
-interfaces are used, adding "l3" changes this to netkit which provide a
+network name. /31 is used for IPv4- and /127 for IPv6-prefixes. If "-" is used
+as net-name then no addresses are assigned (useful for unnumbered links). The
+MAC address is not static and allocated by the kernel. The link is named after
+the node "on the other side". Multiple links can be created between two nodes.
+In this case "_2", "_3", etc. is appended to the interface name. By default
+veth interfaces are used, adding "l3" changes this to netkit which provide a
 layer-3 connection without needing ARP (requires kernel 6.7, iproute2 6.8).
 
 === Option "cmd"
diff --git a/config.go b/config.go
index 2773b8d..11963e6 100644
--- a/config.go
+++ b/config.go
@@ -93,7 +93,7 @@ func LoadConfig(path string) (*Config, error) {
 			usage = `"node" <name> [<loopback-net-name>...]`
 			err = parseConfigNode(&cfg, xs[1:])
 		case "link":
-			usage = `"link" <node> <node> <net-name> ["l3"]`
+			usage = `"link" <node> <node> <net-name>|"-" ["l3"]`
 			err = parseConfigLink(&cfg, xs[1:])
 		case "cmd":
 			usage = `"cmd" <string-passed-to-sh-c>`
@@ -203,17 +203,21 @@ func parseConfigLink(cfg *Config, args []string) error {
 		return fmt.Errorf("node %q does not exist", args[1])
 	}
 
-	n := cfg.Nets[args[2]]
-	if n == nil {
-		return fmt.Errorf("net %q does not exist", args[2])
-	}
-	a1, err := n.Next()
-	if err != nil {
-		return err
-	}
-	a2, err := n.Next()
-	if err != nil {
-		return err
+	var a1, a2 []netip.Addr
+	if args[2] != "-" {
+		n := cfg.Nets[args[2]]
+		if n == nil {
+			return fmt.Errorf("net %q does not exist", args[2])
+		}
+		var err error
+		a1, err = n.Next()
+		if err != nil {
+			return err
+		}
+		a2, err = n.Next()
+		if err != nil {
+			return err
+		}
 	}
 
 	var l Link
-- 
2.49.0