The Network kernel services are divided into the Address Family Domain and Network Interface Device Driver services, Routing and Interface services, Loopback services, Protocol services, and Communications Device Handler Interface services.
The following information is provided to assist you in learning more about network kernel services:
The Address Family Domain and Network Interface Device Driver services enable address family domains (Protocols) and network interface drivers to add and remove themselves from network switch tables.
The if_attach service and if_detach services add and remove network interfaces from the Network Interface List. Protocols search this list to determine an appropriate interface on which to transmit a packet.
Protocols use the add_input_type and del_input_type services to notify network interface drivers that the protocol is available to handle packets of a certain type. The Network Interface Driver uses the find_input_type service to distribute packets to a protocol.
The add_netisr and del_netisr services add and delete network software interrupt handlers. Address families add and delete themselves from the Address Family Domain switch table by using the add_domain_af and del_domain_af services. The Address Family Domain switch table is a list of all available protocols that can be used in the socket subroutine.
The Address Family Domain and Network Interface Device Driver services are:
| add_domain_af | Adds an address family to the Address Family domain switch table. |
| add_input_type | Adds a new input type to the Network Input table. |
| add_netisr | Adds a network software interrupt service to the Network Interrupt table. |
| del_domain_af | Deletes an address family from the Address Family domain switch table. |
| del_input_type | Deletes an input type from the Network Input table. |
| del_netisr | Deletes a network software interrupt service routine from the Network Interrupt table. |
| find_input_type | Finds the given packet type in the Network Input Interface switch table and distributes the input packet according to the table entry for that type. |
| if_attach | Adds a network interface to the network interface list. |
| if_detach | Deletes a network interface from the network interface list. |
| ifunit | Returns a pointer to the ifnet structure of the requested interface. |
| schednetisr | Schedules or invokes a network software interrupt service routine. |
The Routing and Interface Address services provide protocols with a means of establishing, accessing, and removing routes to remote hosts or gateways. Routes bind destinations to a particular network interface.
The interface address services accept a destination address or network and return an associated interface address. Protocols use these services to determine if an address is on a directly connected network.
The Routing and Interface Address services are:
| ifa_ifwithaddr | Locates an interface based on a complete address. |
| ifa_ifwithdstaddr | Locates the point-to-point interface with a given destination address. |
| ifa_ifwithnet | Locates an interface on a specific network. |
| if_down | Marks an interface as down. |
| if_nostat | Zeroes statistical elements of the interface array in preparation for an attach operation. |
| rtalloc | Allocates a route. |
| rtfree | Frees the routing table entry |
| rtinit | Sets up a routing table entry, typically for a network interface. |
| rtredirect | Forces a routing table entry with the specified destination to go through the given gateway. |
| rtrequest | Carries out a request to change the routing table. |
The Loopback services enable networking code to be exercised without actually transmitting packets on a network. This is a useful tool for developing new protocols without introducing network variables. Loopback services can also be used to send packets to local addresses without using hardware loopback.
| loifp | Returns the address of the software loopback interface structure. |
| looutput | Sends data through a software loopback interface. |
Protocol kernel services provide a means of finding a particular address family as well as a raw protocol handler. The raw protocol handler basically passes raw packets up through sockets so that a protocol can be implemented in user space.
The Protocol kernel services are:
| pfctlinput | Starts the ctlinput function for each configured protocol. |
| pffindproto | Returns the address of a protocol switch table entry. |
| raw_input | Builds a raw_header structure for a packet and sends both to the raw protocol handler. |
| raw_usrreq | Implements user requests for raw protocols. |
The Communications Device Handler Interface services provide a standard interface between network interface drivers and communications device handlers. The net_attach and net_detach services open and close the device handler. Once the device handler has been opened, the net_xmit service can be used to transmit packets. Asynchronous start done notifications are recorded by the net_start_done service. The net_error service handles error conditions.
The Communications Device Handler Interface services are:
| add_netopt | This macro adds a network option structure to the list of network options. |
| del_netopt | This macro deletes a network option structure from the list of network options. |
| net_attach | Opens a communications I/O device handler. |
| net_detach | Closes a communications I/O device handler. |
| net_error | Handles errors for communication network interface drivers. |
| net_sleep | Sleeps on the specified wait channel. |
| net_start | Starts network IDs on a communications I/O device handler. |
| net_start_done | Starts the done notification handler for communications I/O device handlers. |
| net_wakeup | Wakes up all sleepers waiting on the specified wait channel. |
| net_xmit | Transmits data using a communications I/O device handler. |
| net_xmit_trace | Traces transmit packets. This kernel service was added for those network interfaces that do not use the net_xmit kernel service to trace transmit packets. |
Communications Physical Device Handler Model Overview.