From 808c5b21c2759564689933d004223052b7895a42 Mon Sep 17 00:00:00 2001 From: Neale Ranns Date: Wed, 2 Aug 2017 05:15:07 -0700 Subject: DHCP Client: receive unicast ACKs despite VPP DHCP client setting neither ciaddr nor giaddr and setting the broadcast bit (see RFC 2131 section 4.1) some DHCP servers will still send a unicast DCHPACK. So as not to drop this VPP must have both 1) a receive FIB entry for the OFFERED IP adress and 2) a 'don't drop me because of uRPF' FIB entry for the DHCP server's address. Change-Id: I167d858deb45629318cbdccf5bf67d971730a42f Signed-off-by: Neale Ranns --- src/vnet/dhcp/client.c | 79 +++++++++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 78 insertions(+), 1 deletion(-) (limited to 'src/vnet/dhcp/client.c') diff --git a/src/vnet/dhcp/client.c b/src/vnet/dhcp/client.c index 25ab3176ae5..cfe62a6f45b 100644 --- a/src/vnet/dhcp/client.c +++ b/src/vnet/dhcp/client.c @@ -22,6 +22,70 @@ static u8 * format_dhcp_client_state (u8 * s, va_list * va); static vlib_node_registration_t dhcp_client_process_node; static void +dhcp_client_add_rx_address (dhcp_client_main_t * dcm, dhcp_client_t * c) +{ + /* Install a local entry for the offered address */ + fib_prefix_t rx = + { + .fp_len = 32, + .fp_addr.ip4 = c->leased_address, + .fp_proto = FIB_PROTOCOL_IP4, + }; + + fib_table_entry_special_add(fib_table_get_index_for_sw_if_index( + FIB_PROTOCOL_IP4, + c->sw_if_index), + &rx, + FIB_SOURCE_DHCP, + (FIB_ENTRY_FLAG_LOCAL)); + + /* And add the server's address as uRPF exempt so we can accept + * local packets from it */ + fib_prefix_t server = + { + .fp_len = 32, + .fp_addr.ip4 = c->dhcp_server, + .fp_proto = FIB_PROTOCOL_IP4, + }; + + fib_table_entry_special_add(fib_table_get_index_for_sw_if_index( + FIB_PROTOCOL_IP4, + c->sw_if_index), + &server, + FIB_SOURCE_URPF_EXEMPT, + (FIB_ENTRY_FLAG_DROP)); +} + +static void +dhcp_client_remove_rx_address (dhcp_client_main_t * dcm, dhcp_client_t * c) +{ + fib_prefix_t rx = + { + .fp_len = 32, + .fp_addr.ip4 = c->leased_address, + .fp_proto = FIB_PROTOCOL_IP4, + }; + + fib_table_entry_special_remove(fib_table_get_index_for_sw_if_index( + FIB_PROTOCOL_IP4, + c->sw_if_index), + &rx, + FIB_SOURCE_DHCP); + fib_prefix_t server = + { + .fp_len = 32, + .fp_addr.ip4 = c->dhcp_server, + .fp_proto = FIB_PROTOCOL_IP4, + }; + + fib_table_entry_special_remove(fib_table_get_index_for_sw_if_index( + FIB_PROTOCOL_IP4, + c->sw_if_index), + &server, + FIB_SOURCE_URPF_EXEMPT); +} + +static void dhcp_client_acquire_address (dhcp_client_main_t * dcm, dhcp_client_t * c) { /* @@ -95,7 +159,9 @@ int dhcp_client_for_us (u32 bi, vlib_buffer_t * b, /* parse through the packet, learn what we can */ if (dhcp->your_ip_address.as_u32) c->leased_address.as_u32 = dhcp->your_ip_address.as_u32; - + + c->dhcp_server.as_u32 = dhcp->server_ip_address.as_u32; + o = (dhcp_option_t *) dhcp->options; while (o->option != 0xFF /* end of options */ && @@ -172,6 +238,14 @@ int dhcp_client_for_us (u32 bi, vlib_buffer_t * b, c->next_transmit = now + 5.0; break; } + /* + * in order to accept unicasted ACKs we need to configure the offered + * address on the interface. However, at this point we may not know the + * subnet-mask (an OFFER may not contain it). So add a temporary receice + * and uRPF excempt entry + */ + dhcp_client_add_rx_address (dcm, c); + /* Received an offer, go send a request */ c->state = DHCP_REQUEST; c->retry_count = 0; @@ -196,6 +270,8 @@ int dhcp_client_for_us (u32 bi, vlib_buffer_t * b, { void (*fp)(u32, u32, u8 *, u8, u8, u8 *, u8 *, u8 *) = c->event_callback; + /* replace the temporary RX address with the correct subnet */ + dhcp_client_remove_rx_address (dcm, c); dhcp_client_acquire_address (dcm, c); /* @@ -831,6 +907,7 @@ int dhcp_client_add_del (dhcp_client_add_del_args_t * a) 1, FIB_ROUTE_PATH_FLAG_NONE); } + dhcp_client_remove_rx_address (dcm, c); dhcp_client_release_address (dcm, c); ip4_sw_interface_enable_disable (c->sw_if_index, 0); -- cgit 1.2.3-korg