How to remove the android OS version from the DHCP request?

Question

When my phone connects to my home WiFi network, it sends DHCP request in order to get an IP address. It looks like the following:



22:50:53.743535 IP (tos 0x10, ttl 64, id 0, offset 0, flags [DF], proto UDP (17), length 328)


 0.0.0.0.68 > 255.255.255.255.67: BOOTP/DHCP, Request from a0:39:f7:5f:c0:45, length 300, xid 0xddd7abec, Flags [none]


 Client-Ethernet-Address a0:39:f7:5f:c0:45


 Vendor-rfc1048 Extensions


Magic Cookie 0x63825363


DHCP-Message Option 53, length 1: Discover


Client-ID Option 61, length 7: ether a0:39:f7:5f:c0:45


MSZ Option 57, length 2: 1500


Vendor-Class Option 60, length 18: "android-dhcp-7.1.2"


Hostname Option 12, length 9: "localhost"


Parameter-Request Option 55, length 10:


  Subnet-Mask, Default-Gateway, Domain-Name-Server, Domain-Name


  MTU, BR, Lease-Time, RN


  RB, Vendor-Option


As you can see, there's Vendor-Class Option 60, length 18: "android-dhcp-7.1.2" which contains the OS version. Is there a way to remove this from the request?


— Mikhail Morfikov | Sources

Answer

It's hard-coded in Java DhcpClient:



...


 private String getVendorId() {



  if (testOverrideVendorId != null) return testOverrideVendorId;


  return "android-dhcp-" + Build.VERSION.RELEASE;


 
}


...


So the only way is to rebuild your ROM with modified source code. Or use a different DHCP client from command-line. For reference: Connecting to WiFi via ADB Shell.


— Irfan Latif | Sources

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