From a73bf976975bba11b0456d32b565fefcceff8906 Mon Sep 17 00:00:00 2001
From: GnomeZworc <nicolas.boufidjeline@g3e.fr>
Date: Sun, 4 Oct 2026 19:56:42 +0200
Subject: [PATCH] f-51: netif: poser l'adresse VTEP locale des VXLAN #51

Signed-off-by: GnomeZworc <nicolas.boufidjeline@g3e.fr>
---
 internal/netif/vxlan.go      | 28 ++++++++++++++++
 internal/netif/vxlan_test.go | 64 ++++++++++++++++++++++++++++++++++++
 2 files changed, 92 insertions(+)
 create mode 100644 internal/netif/vxlan_test.go

diff --git a/internal/netif/vxlan.go b/internal/netif/vxlan.go
index 70740bc..0930cb3 100644
--- a/internal/netif/vxlan.go
+++ b/internal/netif/vxlan.go
@@ -1,14 +1,31 @@
 package netif
 
 import (
+	"fmt"
+	"net"
+	"syscall"
+
 	"github.com/vishvananda/netlink"
 )
 
+const (
+	scopeUniverse    = 0
+	addressSecondary = 0x01
+)
+
 func CreateVxlan(name string, vxlanID int, localIface string, mtu int) error {
 	link, err := netlink.LinkByName(localIface)
 	if err != nil {
 		return err
 	}
+	addrs, err := netlink.AddrList(link, syscall.AF_INET)
+	if err != nil {
+		return err
+	}
+	local, err := vtepAddress(localIface, addrs)
+	if err != nil {
+		return err
+	}
 	vxlan := &netlink.Vxlan{
 		LinkAttrs: netlink.LinkAttrs{
 			Name: name,
@@ -17,7 +34,18 @@ func CreateVxlan(name string, vxlanID int, localIface string, mtu int) error {
 		VxlanId:      vxlanID,
 		Port:         4789,
 		VtepDevIndex: link.Attrs().Index,
+		SrcAddr:      local,
 		Learning:     false,
 	}
 	return netlink.LinkAdd(vxlan)
 }
+
+func vtepAddress(iface string, addrs []netlink.Addr) (net.IP, error) {
+	for _, a := range addrs {
+		if a.IPNet == nil || a.IP.To4() == nil || a.Scope != scopeUniverse || a.Flags&addressSecondary != 0 {
+			continue
+		}
+		return a.IP.To4(), nil
+	}
+	return nil, fmt.Errorf("no primary global IPv4 address on %s for the VXLAN local endpoint", iface)
+}
diff --git a/internal/netif/vxlan_test.go b/internal/netif/vxlan_test.go
new file mode 100644
index 0000000..6ea7ca4
--- /dev/null
+++ b/internal/netif/vxlan_test.go
@@ -0,0 +1,64 @@
+package netif
+
+import (
+	"net"
+	"strings"
+	"testing"
+
+	"github.com/vishvananda/netlink"
+)
+
+func addr(cidr string, scope, flags int) netlink.Addr {
+	ip, network, err := net.ParseCIDR(cidr)
+	if err != nil {
+		panic(err)
+	}
+	network.IP = ip
+	return netlink.Addr{IPNet: network, Scope: scope, Flags: flags}
+}
+
+func TestVtepAddress_PicksThePrimaryGlobalIPv4(t *testing.T) {
+	addrs := []netlink.Addr{
+		addr("127.0.0.1/8", 254, 0),
+		addr("169.254.0.3/28", 0, 0x01),
+		addr("192.168.14.11/24", 0, 0x80),
+		addr("192.168.14.99/24", 0, 0x01),
+	}
+	got, err := vtepAddress("br-000000", addrs)
+	if err != nil || got.String() != "192.168.14.11" {
+		t.Errorf("vtepAddress = %v, %v, want 192.168.14.11", got, err)
+	}
+}
+
+func TestVtepAddress_SkipsLinkScopeAndSecondaryAddresses(t *testing.T) {
+	addrs := []netlink.Addr{
+		addr("169.254.0.3/28", 253, 0),
+		addr("192.168.14.99/24", 0, 0x01),
+		addr("192.168.14.12/24", 0, 0),
+	}
+	got, err := vtepAddress("br-000000", addrs)
+	if err != nil || got.String() != "192.168.14.12" {
+		t.Errorf("vtepAddress = %v, %v, want 192.168.14.12", got, err)
+	}
+}
+
+func TestVtepAddress_RefusesAnInterfaceWithoutUsableAddress(t *testing.T) {
+	for name, addrs := range map[string][]netlink.Addr{
+		"no address":     nil,
+		"only secondary": {addr("192.168.14.99/24", 0, 0x01)},
+		"only link":      {addr("169.254.0.3/28", 253, 0)},
+		"only IPv6":      {addr("fd00::11/64", 0, 0)},
+	} {
+		_, err := vtepAddress("br-000000", addrs)
+		if err == nil || !strings.Contains(err.Error(), "no primary global IPv4 address on br-000000") {
+			t.Errorf("%s: error = %v", name, err)
+		}
+	}
+}
+
+func TestVtepAddress_ReturnsAFourByteAddress(t *testing.T) {
+	got, err := vtepAddress("br-000000", []netlink.Addr{addr("192.168.14.11/24", 0, 0)})
+	if err != nil || len(got) != 4 {
+		t.Errorf("vtepAddress = %v (%d bytes), %v", got, len(got), err)
+	}
+}