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- dhcp: CheckIfOtherDHCPServersPresent: fix

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Sometimes request from DHCP server couldn't be received
 because we were bound to a specific IP address.
This commit is contained in:
Simon Zolin
2020-08-12 18:13:07 +03:00
parent 6090400ea0
commit 23752377b7
3 changed files with 10 additions and 94 deletions
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15
dhcpd/check_other_dhcp.go
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@@ -7,12 +7,13 @@ import (
"fmt"
"net"
"os"
"runtime"
"time"
"github.com/AdguardTeam/golibs/log"
"github.com/insomniacslk/dhcp/dhcpv4"
"github.com/insomniacslk/dhcp/dhcpv4/nclient4"
"github.com/insomniacslk/dhcp/iana"
"golang.org/x/net/ipv4"
)
// CheckIfOtherDHCPServersPresent sends a DHCP request to the specified network interface,
@@ -29,6 +30,10 @@ func CheckIfOtherDHCPServersPresent(ifaceName string) (bool, error) {
return false, fmt.Errorf("couldn't find IPv4 address of interface %s %+v", ifaceName, iface)
}
if runtime.GOOS == "darwin" {
return false, fmt.Errorf("Can't find DHCP server: not supported on macOS")
}
srcIP := ifaceIPNet[0]
src := net.JoinHostPort(srcIP.String(), "68")
dst := "255.255.255.255:67"
@@ -60,7 +65,7 @@ func CheckIfOtherDHCPServersPresent(ifaceName string) (bool, error) {
// bind to 0.0.0.0:68
log.Tracef("Listening to udp4 %+v", udpAddr)
c, err := newBroadcastPacketConn(net.IPv4(0, 0, 0, 0), 68, ifaceName)
c, err := nclient4.NewRawUDPConn(ifaceName, 68)
if c != nil {
defer c.Close()
}
@@ -69,8 +74,7 @@ func CheckIfOtherDHCPServersPresent(ifaceName string) (bool, error) {
}
// send to 255.255.255.255:67
cm := ipv4.ControlMessage{}
_, err = c.WriteTo(req.ToBytes(), &cm, dstAddr)
_, err = c.WriteTo(req.ToBytes(), dstAddr)
if err != nil {
return false, wrapErrPrint(err, "Couldn't send a packet to %s", dst)
}
@@ -81,9 +85,10 @@ func CheckIfOtherDHCPServersPresent(ifaceName string) (bool, error) {
// TODO: replicate dhclient's behaviour of retrying several times with progressively bigger timeouts
b := make([]byte, 1500)
_ = c.SetReadDeadline(time.Now().Add(defaultDiscoverTime))
n, _, _, err := c.ReadFrom(b)
n, _, err := c.ReadFrom(b)
if isTimeout(err) {
// timed out -- no DHCP servers
log.Debug("DHCPv4: didn't receive DHCP response")
return false, nil
}
if err != nil {