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kvm
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fix(net): stop dhcp client and release all v4 addr on linkdown (#16) 

This commit fixes jetkvm/kvm#12 by disabling the udhcpc client when the
link goes down, it then removes all the active IPv4 addresses from the
deivce.

Once the link comes back up, it re-activates the udhcpc client so it can
fetch a new IPv4 address for the device.

This doesn't make any changes to the IPv6 side of things yet.
This commit is contained in:
Cameron Fleming 2025-02-13 14:41:10 +00:00 committed by GitHub
parent 0b5033f798
commit 2a99c2db9d
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GPG Key ID: B5690EEEBB952194
1 changed files with 36 additions and 1 deletions
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35
network.go
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@ -6,6 +6,7 @@ import (
"golang.org/x/net/ipv4"
"golang.org/x/net/ipv6"
"net"
"os/exec"
"time"
"github.com/vishvananda/netlink"
@ -25,6 +26,23 @@ type LocalIpInfo struct {
MAC string
}
// setDhcpClientState sends signals to udhcpc to change it's current mode
// of operation. Setting active to true will force udhcpc to renew the DHCP lease.
// Setting active to false will put udhcpc into idle mode.
func setDhcpClientState(active bool) {
var signal string;
if active {
signal = "-SIGUSR1"
} else {
signal = "-SIGUSR2"
}
cmd := exec.Command("/usr/bin/killall", signal, "udhcpc");
if err := cmd.Run(); err != nil {
fmt.Printf("network: setDhcpClientState: failed to change udhcpc state: %s\n", err)
}
}
func checkNetworkState() {
iface, err := netlink.LinkByName("eth0")
if err != nil {
@ -47,9 +65,26 @@ func checkNetworkState() {
fmt.Printf("failed to get addresses for eth0: %v\n", err)
}
// If the link is going down, put udhcpc into idle mode.
// If the link is coming back up, activate udhcpc and force it to renew the lease.
if newState.Up != networkState.Up {
setDhcpClientState(newState.Up)
}
for _, addr := range addrs {
if addr.IP.To4() != nil {
if !newState.Up && networkState.Up {
// If the network is going down, remove all IPv4 addresses from the interface.
fmt.Printf("network: state transitioned to down, removing IPv4 address %s\n", addr.IP.String())
err := netlink.AddrDel(iface, &addr)
if err != nil {
fmt.Printf("network: failed to delete %s", addr.IP.String())
}
newState.IPv4 = "..."
} else {
newState.IPv4 = addr.IP.String()
}
} else if addr.IP.To16() != nil && newState.IPv6 == "" {
newState.IPv6 = addr.IP.String()
}