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etharp_query() function
Send an ARP request for the given IP address and/or queue a packet. If the IP address was not yet in the cache, a pending ARP cache entry is added and an ARP request is sent for the given address. The packet is queued on this entry. If the IP address was already pending in the cache, a new ARP request is sent for the given address. The packet is queued on this entry. If the IP address was already stable in the cache, and a packet is given, it is directly sent and no ARP request is sent out. If the IP address was already stable in the cache, and no packet is given, an ARP request is sent out.
Syntax
Implemented in ![]()
etharp.c:932
Return value
- ERR_BUF Could not make room for Ethernet header. - ERR_MEM Hardware address unknown, and no more ARP entries available to query for address or queue the packet. - ERR_MEM Could not queue packet due to memory shortage. - ERR_RTE No route to destination (no gateway to external networks). - ERR_ARG Non-unicast address given, those will not appear in ARP cache.
Notes
q must only be ONE packet, not a packet queue!
Related Functions
Found 75 other functions taking a ![]()
netif
argument:
Function
Description
Bring an interface down, disabling any traffic processing.
Bring an interface up, available for processing traffic.
Called by a driver when its link goes up
Called by a driver when its link goes down
Start DHCP negotiation for a network interface. If no DHCP client instance was attached to this interface, a new client is created first. If a DHCP client instance was already present, it restarts negotiation.
Add a network interface to the list of lwIP netifs.
Set a network interface as the default network interface (used to output all packets for which no specific route is found)
Resolve and fill-in Ethernet address header for outgoing IP packet. For IP multicast and broadcast, corresponding Ethernet addresses are selected and the packet is transmitted on the link. For unicast addresses, the packet is submitted to etharp_query(). In case the IP address is outside the local network, the IP address of the gateway is used.
Change IP address configuration for a network interface (including netmask and default gateway).
check if DHCP supplied netif->ip_addr
Set callback to be called when link is brought up/down
Process received ethernet frames. Using this function instead of directly calling ip_input and passing ARP frames through etharp in ethernetif_input, the ARP cache is protected from concurrent access.\n Don't call directly, pass to netif_add() and call netif->input(). @see LWIP_HOOK_UNKNOWN_ETH_PROTOCOL @see ETHARP_SUPPORT_VLAN @see LWIP_HOOK_VLAN_CHECK
Pass a received packet to tcpip_thread for input processing with ethernet_input or ip_input. Don't call directly, pass to netif_add() and call netif->input().
Determine if an address is a broadcast address on a network interface
Create a DHCP request, fill in common headers
Send data to a specified address using UDP. The netif used for sending can be specified. This function exists mainly for DHCP, to be able to send UDP packets on a netif that is still down. dst_ip & dst_port are expected to be in the same byte order as in the pcb. @see udp_disconnect() udp_send()
Sends an IP packet on a network interface. This function constructs the IP header and calculates the IP header checksum. If the source IP address is NULL, the IP address of the outgoing network interface is filled in as source address. If the destination IP address is LWIP_IP_HDRINCL, p is assumed to already include an IP header and p->payload points to it instead of the data.
Release a DHCP lease and stop DHCP statemachine (and AUTOIP if LWIP_DHCP_AUTOIP_COOP).
Send an ethernet packet on the network using netif->linkoutput(). The ethernet header is filled in before sending. @see LWIP_HOOK_VLAN_SET
Start the DHCP process, discover a DHCP server.
Same as udp_sendto_if, but with source address
Send an ARP request packet asking for ipaddr.
Calculates the effective send mss that can be used for a specific IP address by calculating the minimum of TCP_MSS and the mtu (if set) of the target netif (if not NULL).
This function is called by the network interface device driver when an IP packet is received. The function does the basic checks of the IP header such as packet size being at least larger than the header size etc. If the packet was not destined for us, the packet is forwarded (using ip_forward). The IP checksum is always checked. Finally, the packet is sent to the upper layer protocol input function.
Send ARP/IGMP/MLD/RS events, e.g. on link-up/netif-up or addr-change
Bind the interface to the offered IP address.
Same as ip_output_if() but 'src' address is not replaced by netif address when it is 'any'.
Bind an UDP PCB to a specific netif. After calling this function, all packets received via this PCB are guaranteed to have come in via the specified netif, and all outgoing packets will go out via the specified netif. @see udp_disconnect()
Pass a received packet to tcpip_thread for input processing
Binds the connection to a netif and IP address. After calling this function, all packets received via this PCB are guaranteed to have come in via the specified netif, and all outgoing packets will go out via the specified netif.
Select a DHCP server offer out of all offers. Simply select the first offer received.
Enter REBOOTING state to verify an existing lease
Search the ARP table for a matching or new entry. If an IP address is given, return a pending or stable ARP entry that matches the address. If no match is found, create a new entry with this address set, but in state ETHARP_EMPTY. The caller must check and possibly change the state of the returned entry. If ipaddr is NULL, return a initialized new entry in state ETHARP_EMPTY. In all cases, attempt to create new entries from an empty entry. If no empty entries are available and ETHARP_FLAG_TRY_HARD flag is set, recycle old entries. Heuristic choose the least important entry for recycling.
Send an ARP request packet asking for ipaddr to a specific eth address. Used to send unicast request to refresh the ARP table just before an entry times out
Send a raw ARP packet (opcode and all addresses can be modified)
Process an incoming UDP datagram. Given an incoming UDP datagram (as a chain of pbufs) this function finds a corresponding UDP PCB and hands over the pbuf to the pcbs recv function. If no pcb is found or the datagram is incorrect, the pbuf is freed.
Renew an existing DHCP lease at the involved DHCP server.
This function calls dhcp_release_and_stop() internally. @deprecated Use dhcp_release_and_stop() instead.
Handle a possible change in the network configuration. This enters the REBOOTING state to verify that the currently bound address is still valid.
Match an ARP reply with the offered IP address: check whether the offered IP address is not in use using ARP
Remove all ARP table entries of the specified netif.
Responds to ARP requests to us. Upon ARP replies to us, add entry to cache send out queued IP packets. Updates cache with snooped address pairs. Should be called for incoming ARP packets. The pbuf in the argument is freed by this function. @see pbuf_free()
The initial input processing of TCP. It verifies the TCP header, demultiplexes the segment between the PCBs and passes it on to tcp_process(), which implements the TCP finite state machine. This function is called by the IP layer (in ip_input()).
Processes ICMP input packets, called from ip_input(). Currently only processes icmp echo requests and sends out the echo response.
Fragment an IP datagram if too large for the netif. Chop the datagram in MTU sized chunks and send them in order by pointing PBUF_REFs into p.
Dummy IPv4 output function for netifs not supporting IPv4
Called by tcp_output() to actually send a TCP segment over IP.
Checks if the offered IP address is already in use. It does so by sending an ARP request for the offered address and entering CHECKING state. If no ARP reply is received within a small interval, the address is assumed to be free for use by us.
A DHCP negotiation transaction, or ARP request, has timed out. The timer that was started with the DHCP or ARP request has timed out, indicating no response was received in time.
The renewal period has timed out.
The rebind period has timed out.
Handle a DHCP ACK packet
Rebind with a DHCP server for an existing DHCP lease.
Decline an offered lease. Tell the DHCP server we do not accept the offered address. One reason to decline the lease is when we find out the address is already in use by another host (through ARP).
Just a small helper function that sends a pbuf to an ethernet address in the arp_table specified by the index 'arp_idx'.
Return true if the current input packet should be accepted on this netif
Add a network interface to the list of lwIP netifs. Same as netif_add but without IPv4 addresses
Remove a network interface from the list of lwIP netifs.
Change the IP address of a network interface
Change the netmask of a network interface
Change the default gateway for a network interface
Forwards a received packet for input processing with ethernet_input() or ip_input() depending on netif flags. Don't call directly, pass to netif_add() and call netif->input(). Only works if the netif driver correctly sets NETIF_FLAG_ETHARP and/or NETIF_FLAG_ETHERNET flag!
Set a statically allocated struct dhcp to work with. Using this prevents dhcp_start to allocate it using mem_malloc.
Removes a struct dhcp from a netif. ATTENTION: Only use this when not using dhcp_set_struct() to allocate the struct dhcp since the memory is passed back to the heap.
This function calls dhcp_release_and_stop() internally. @deprecated Use dhcp_release_and_stop() instead.
Inform a DHCP server of our manual configuration. This informs DHCP servers of our fixed IP address configuration by sending an INFORM message. It does not involve DHCP address configuration, it is just here to be nice to the network.
Finds (stable) ethernet/IP address pair from ARP table using interface and IP address index.
Possibility to iterate over stable ARP table entries
Common code to see if the current input packet matches the pcb (current input packet is accessed via ip(4/6)_current_* macros)
Remember the configuration offered by a DHCP server.
Back-off the DHCP client (because of a received NAK response). Back-off the DHCP client because of a received NAK. Receiving a NAK means the client asked for something non-sensible, for example when it tries to renew a lease obtained on another network. We clear any existing set IP address and restart DHCP negotiation afresh (as per RFC2131 3.2.3).
Update (or insert) a IP/MAC address pair in the ARP cache. If a pending entry is resolved, any queued packets will be sent at this point. @see pbuf_free()