DHCP Client: DHCPNAK behavior

[Vitaliy Orazov]

Hi!
 
Faced with the issue of not responding to DHCPNAK  from another server , I then compared the behavior between busybox  udhcp client and  isc dhclient when receiving DHCPNAK. And behaviors are different. Your client checks for server_id matching, this check was introduced for the fix,  Bug 4267 .
But in  isc dhclient there is no check for server_id and it seems to me correct, because in  rfc2131 I did not find requirements for matching server_id in the request for the client, but I found the following text:
RFC 2131   [Page 17]
If the client receives a DHCPNAK message, the client restarts the
     configuration process.
 
Here is another piece of text from  rfc2131 , which I believe points to the key moment of using server_id in the client:
RFC 2131   [Page 23]
DHCP clients MUST
   use the IP address provided in the 'server identifier' option for any
   unicast requests to the DHCP server.
 
this is also consistent with  rfc2132 :
RFC 2132   [Page 27]
DHCP clients use the
   contents of the 'server identifier' field as the destination address
   for any DHCP messages unicast to the DHCP server.
 
 
PS.  Bug 14456
 
Best Regards
Vitaliy Orazov
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