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Add support detecting the request for a specific IP address over DHCP

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This commit is contained in:
maride 2019-11-28 19:16:43 +01:00
parent f918d26ab5
commit c01d1f49c2
2 changed files with 19 additions and 3 deletions
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21
ethernet/dhcpv4/dhcp.go
View File

@ -45,7 +45,7 @@ func HandleDHCPv4Packet(packet gopacket.Packet) error {
appendIfUnique(dhcppacket.ClientHWAddr.String(), requestMAC)
} else {
// Response/Offer packet
addResponseEntry(dhcppacket.ClientIP.String(), dhcppacket.ClientHWAddr.String(), ethernetpacket.SrcMAC.String())
addResponseEntry(dhcppacket.ClientIP.String(), dhcppacket.YourClientIP.String(), dhcppacket.ClientHWAddr.String(), ethernetpacket.SrcMAC.String())
}
return nil
@ -72,7 +72,13 @@ func printResponseSummary() {
// Iterate over all responses
for _, r := range responses {
tmpaddr = append(tmpaddr, fmt.Sprintf("%s offered %s IP address %s", r.serverMACAddr, r.destMACAddr, r.newIPAddr))
addition := ""
if r.askedFor {
addition = " which the client explicitly asked for."
}
tmpaddr = append(tmpaddr, fmt.Sprintf("%s offered %s IP address %s%s", r.serverMACAddr, r.destMACAddr, r.newIPAddr, addition))
}
// Draw as tree
@ -80,7 +86,15 @@ func printResponseSummary() {
}
// Adds a new response entry. If an IP address was already issued or a MAC asks multiple times for DNS, the case is examined further
func addResponseEntry(newIP string, destMAC string, serverMAC string) {
func addResponseEntry(newIP string, yourIP string, destMAC string, serverMAC string) {
// Check if client asked for a specific address (which was granted by the DHCP server)
askedFor := false
if newIP == "0.0.0.0" {
// Yes, client asked for a specific address. Most likely not the first time in this network.
newIP = yourIP
askedFor = true
}
for _, r := range responses {
// Check for interesting cases
if r.destMACAddr == destMAC {
@ -112,5 +126,6 @@ func addResponseEntry(newIP string, destMAC string, serverMAC string) {
destMACAddr: destMAC,
newIPAddr: newIP,
serverMACAddr: serverMAC,
askedFor: askedFor,
})
}

1
ethernet/dhcpv4/dhcpResponse.go
View File

@ -4,5 +4,6 @@ type dhcpResponse struct {
destMACAddr string
newIPAddr string
serverMACAddr string
askedFor bool
}