diff options
| -rw-r--r-- | networking/udhcp/clientpacket.c | 13 | ||||
| -rw-r--r-- | networking/udhcp/dhcpd.c | 101 |
2 files changed, 93 insertions, 21 deletions
diff --git a/networking/udhcp/clientpacket.c b/networking/udhcp/clientpacket.c index a0be428..b4a75be 100644 --- a/networking/udhcp/clientpacket.c +++ b/networking/udhcp/clientpacket.c @@ -156,20 +156,7 @@ int FAST_FUNC send_renew(uint32_t xid, uint32_t server, uint32_t ciaddr) init_packet(&packet, DHCPREQUEST); packet.xid = xid; - /* RFC 2131: - * "3.2 Client-server interaction - reusing a previously - * allocated network address"... - * The client broadcasts a DHCPREQUEST message on its local subnet. - * The message includes the client's network address in the - * REQUESTED_IP option. As the client has not received its - * network address, it MUST NOT fill in the 'ciaddr' field." - * - * FIXME: we seem to not follow this, we do set ciaddr. - */ packet.ciaddr = ciaddr; - add_simple_option(packet.options, DHCP_REQUESTED_IP, ciaddr); - if (server) - add_simple_option(packet.options, DHCP_SERVER_ID, server); add_param_req_option(&packet); bb_info_msg("Sending renew..."); diff --git a/networking/udhcp/dhcpd.c b/networking/udhcp/dhcpd.c index a529e1b..d6e90cd 100644 --- a/networking/udhcp/dhcpd.c +++ b/networking/udhcp/dhcpd.c @@ -48,7 +48,7 @@ static void send_packet_to_client(struct dhcp_packet *dhcp_pkt, int force_broadc if (force_broadcast || (dhcp_pkt->flags & htons(BROADCAST_FLAG)) - || !dhcp_pkt->ciaddr + || dhcp_pkt->ciaddr == 0 ) { log1("Broadcasting packet to client"); ciaddr = INADDR_BROADCAST; @@ -466,16 +466,101 @@ int udhcpd_main(int argc UNUSED_PARAM, char **argv) case DHCPREQUEST: log1("Received REQUEST"); - - /* RFC 2131: "The REQUESTED_IP option MUST be set - * to the value of 'yiaddr' in the DHCPOFFER message - * from the server." */ +/* RFC 2131: + +o DHCPREQUEST generated during SELECTING state: + + Client inserts the address of the selected server in 'server + identifier', 'ciaddr' MUST be zero, 'requested IP address' MUST be + filled in with the yiaddr value from the chosen DHCPOFFER. + + Note that the client may choose to collect several DHCPOFFER + messages and select the "best" offer. The client indicates its + selection by identifying the offering server in the DHCPREQUEST + message. If the client receives no acceptable offers, the client + may choose to try another DHCPDISCOVER message. Therefore, the + servers may not receive a specific DHCPREQUEST from which they can + decide whether or not the client has accepted the offer. + +o DHCPREQUEST generated during INIT-REBOOT state: + + 'server identifier' MUST NOT be filled in, 'requested IP address' + option MUST be filled in with client's notion of its previously + assigned address. 'ciaddr' MUST be zero. The client is seeking to + verify a previously allocated, cached configuration. Server SHOULD + send a DHCPNAK message to the client if the 'requested IP address' + is incorrect, or is on the wrong network. + + Determining whether a client in the INIT-REBOOT state is on the + correct network is done by examining the contents of 'giaddr', the + 'requested IP address' option, and a database lookup. If the DHCP + server detects that the client is on the wrong net (i.e., the + result of applying the local subnet mask or remote subnet mask (if + 'giaddr' is not zero) to 'requested IP address' option value + doesn't match reality), then the server SHOULD send a DHCPNAK + message to the client. + + If the network is correct, then the DHCP server should check if + the client's notion of its IP address is correct. If not, then the + server SHOULD send a DHCPNAK message to the client. If the DHCP + server has no record of this client, then it MUST remain silent, + and MAY output a warning to the network administrator. This + behavior is necessary for peaceful coexistence of non- + communicating DHCP servers on the same wire. + + If 'giaddr' is 0x0 in the DHCPREQUEST message, the client is on + the same subnet as the server. The server MUST broadcast the + DHCPNAK message to the 0xffffffff broadcast address because the + client may not have a correct network address or subnet mask, and + the client may not be answering ARP requests. + + If 'giaddr' is set in the DHCPREQUEST message, the client is on a + different subnet. The server MUST set the broadcast bit in the + DHCPNAK, so that the relay agent will broadcast the DHCPNAK to the + client, because the client may not have a correct network address + or subnet mask, and the client may not be answering ARP requests. + +o DHCPREQUEST generated during RENEWING state: + + 'server identifier' MUST NOT be filled in, 'requested IP address' + option MUST NOT be filled in, 'ciaddr' MUST be filled in with + client's IP address. In this situation, the client is completely + configured, and is trying to extend its lease. This message will + be unicast, so no relay agents will be involved in its + transmission. Because 'giaddr' is therefore not filled in, the + DHCP server will trust the value in 'ciaddr', and use it when + replying to the client. + + A client MAY choose to renew or extend its lease prior to T1. The + server may choose not to extend the lease (as a policy decision by + the network administrator), but should return a DHCPACK message + regardless. + +o DHCPREQUEST generated during REBINDING state: + + 'server identifier' MUST NOT be filled in, 'requested IP address' + option MUST NOT be filled in, 'ciaddr' MUST be filled in with + client's IP address. In this situation, the client is completely + configured, and is trying to extend its lease. This message MUST + be broadcast to the 0xffffffff IP broadcast address. The DHCP + server SHOULD check 'ciaddr' for correctness before replying to + the DHCPREQUEST. + + The DHCPREQUEST from a REBINDING client is intended to accommodate + sites that have multiple DHCP servers and a mechanism for + maintaining consistency among leases managed by multiple servers. + A DHCP server MAY extend a client's lease only if it has local + administrative authority to do so. +*/ if (!requested_opt) { - log1("no requested IP, ignoring"); - break; + requested_nip = packet.ciaddr; + if (requested_nip == 0) { + log1("no requested IP and no ciaddr, ignoring"); + break; + } } if (lease && requested_nip == lease->lease_nip) { - /* client requests IP which matches the lease. + /* client requested or configured IP matches the lease. * ACK it, and bump lease expiration time. */ send_ACK(&packet, lease->lease_nip); break; |