From 79e91b25c1ee99611f4f40f84cab34e92e3467c3 Mon Sep 17 00:00:00 2001
From: Jacob Weinstock <jakobweinstock@gmail.com>
Date: Wed, 25 Jan 2023 21:03:49 -0700
Subject: [PATCH] Update vlan checking:

Hook creates the vlan interface so we don't need
to create it here.

Signed-off-by: Jacob Weinstock <jakobweinstock@gmail.com>
---
 actions/writefile/v1/main.go | 41 ++++++++----------------------------
 1 file changed, 9 insertions(+), 32 deletions(-)

diff --git a/actions/writefile/v1/main.go b/actions/writefile/v1/main.go
index d2a5ff2..018c2a7 100644
--- a/actions/writefile/v1/main.go
+++ b/actions/writefile/v1/main.go
@@ -14,6 +14,7 @@ import (
 	"os/exec"
 	"path"
 	"path/filepath"
+	"regexp"
 	"runtime"
 	"strconv"
 	"strings"
@@ -23,7 +24,6 @@ import (
 	"github.com/insomniacslk/dhcp/dhcpv4"
 	"github.com/insomniacslk/dhcp/dhcpv4/nclient4"
 	log "github.com/sirupsen/logrus"
-	"github.com/vishvananda/netlink"
 	"github.com/vishvananda/netns"
 )
 
@@ -109,9 +109,9 @@ func main() {
 				log.Errorf("Invalid DHCP_TIMEOUT: %s, using default: %v", t, timeout)
 			}
 		}
-		if name, template, err := vlanEnabled("/proc/cmdline"); err == nil {
+		if n, template, err := vlanEnabled("/proc/cmdline"); err == nil {
 			netplanTemplate = template
-			ifname = name
+			ifname = n
 		}
 		contents, err = dhcpAndWriteNetplan(ifname, timeout, netplanTemplate)
 		if err != nil {
@@ -415,36 +415,13 @@ func ensureDir(mountPath, path string, mode os.FileMode, uid, gid int) error {
 }
 
 func vlanEnabled(f string) (ifname, netplanTemplate string, err error) {
-	cmdline, err := ioutil.ReadFile(f)
-	if err != nil {
-		return "", "", fmt.Errorf("failed to read /proc/cmdline: %w", err)
-	}
-	var vlan int
-	if vlan, err = getVLANID(string(cmdline)); err == nil {
-		// create new interface with vlan id
-		l := netlink.NewLinkAttrs()
-		parent := determineNetIF()
-		n, err := net.InterfaceByName(parent)
-		if err != nil {
-			return "", "", err
-		}
-
-		ifname = fmt.Sprintf(parent+".%d", vlan)
-		l.Name = ifname
-		l.ParentIndex = n.Index
-		link := &netlink.Vlan{LinkAttrs: l, VlanId: vlan, VlanProtocol: netlink.VLAN_PROTOCOL_8021Q}
-		// creat vlan interface
-		if err = netlink.LinkAdd(link); err != nil {
-			return "", "", err
-		}
-		// set interface up
-		if err = netlink.LinkSetUp(link); err != nil {
-			return "", "", err
-		}
-	} else {
-		return "", "", err
+	ifname = determineNetIF()
+	// want "eth0.X", where X is between 1 and 4096
+	// This interface will exist if Hook creates it. Hook will create it if "vlan_id" is set in /proc/cmdline.
+	exp := `^eth0.(409[0-6]|(40[0-8]|[1-3]\d\d|[1-9]\d|[1-9])\d|[1-9])$`
+	if match, err := regexp.MatchString(exp, ifname); err != nil || !match {
+		return "", "", fmt.Errorf("failed to match interface name %s with regex %s: %w", ifname, exp, err)
 	}
-
 	netplanTemplate = `network:
     version: 2
     renderer: networkd
-- 
2.34.1