[GitHub] [incubator-nuttx-apps] normanr commented on pull request #904: netutils/dhcpc: add non-blocking interface

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normanr commented on PR #904:
URL: https://github.com/apache/incubator-nuttx-apps/pull/904#issuecomment-1179452650

   > * sometimes it sees a double-offer, it it will decline it even if it's just a duplicate of the offer that it's just received.
   
   I noticed that this is _not_ how [RFC 2131](https://datatracker.ietf.org/doc/html/rfc2131) intends the client to behave. An `OFFER` is only supposed to be `DECLINED` "If the client detects that the address is already in use (e.g., through the use of ARP)" (and only at the `ACK` stage of processing. If multiple offers are received then the client indicates which server's offer it is accepting through the `server identifier` field.
   
   I also discovered that if any other udp packets arrive at the client while it's sleeping (e.g. from _other_ clients on the same network doing dhcp requests), then they will consume IO buffers, and never give them up, because `dhcpc_request` doesn't expect responses to be queued at the socket. This ends up starving all other network connections on the system. Changing the sleep into a recv & discard loop fixes this.


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