Internal Functions
10.2IP routines
The IP routines are located in various files in the inet directory and are as follows:
•ip_write() on page 10-5
•ip2mac() on page 10-6
•ip_mymach() on page 10-7
•iproute() on page 10-8
•add_route() on page 10-9
•ip_rcv() on page 10-10
•parse_ipad() on page 10-11
•pk_alloc() on page 10-12
•pk_free() on page 10-13.
10-4 |
Copyright © 1998-2001 ARM Limited. All rights reserved. |
ARM DUI 0144B |
Internal Functions
10.2.1ip_write()
The ip_write() routine fills in the Internet header in the packet and sends the packet through the appropriate net interface.
Syntax
int ip_write(u_char prot, PACKET p); where:
prot |
Indicates which protocol the packet is carrying (TCP, UDP, ICMP). |
p |
Is the packet to send. |
Usage
This routine uses routing. You call it with the p->nb_plen and p->nb_prot fields set to the start of the upper (UDP) layer, and with the p->fhost field set to the target IP address.
Return values
Return one of the following:
0 |
If the transmission was successful. |
ENP_SEND_PENDING |
|
|
If it is waiting for ARP. |
ENP_ code |
If an error is detected (see ENP_ error codes on page A-2). |
Location
The ip_write() routine is found in the following file:
inet\ip.c
ARM DUI 0144B |
Copyright © 1998-2001 ARM Limited. All rights reserved. |
10-5 |
Internal Functions
10.2.2ip2mac()
The ip2mac() routine takes as input an outgoing IP packet with no MAC information and tries to resolve an Ethernet address matching the passed IP address.
Syntax
int ip2mac(PACKET pkt, ip_addr dest_ip);
where:
pkt |
Is the packet itself, without the MAC address |
dest_ip Is the IP address of the host or gateway.
Usage
If the MAC address is not already cached, an ARP request is broadcast for the missing IP address. The packet is then attached to the pending pointer. The packet is sent when the ARP reply comes in, or it is freed if the request times out.
Return values
Returns one of the following values:
SUCCESS (0)
If the packet was sent.
ENP_SEND_PENDING
If awaiting the ARP reply.
SEND_FAILED
If an error was detected.
Location
The ip2mac() routine is found in the following file:
inet/ipnet.c
10-6 |
Copyright © 1998-2001 ARM Limited. All rights reserved. |
ARM DUI 0144B |
Internal Functions
10.2.3ip_mymach()
The ip_mymach() routine returns the address of your machine, relative to a given foreign host IP address.
Syntax
ip_addr ip_mymach(ip_addr host);
where:
host |
Is the IP address of the foreign host. |
Usage
On a single-home host, this always returns the IP address of the sole interface. On a router, it returns the address of the interface where packets for the host are routed.
Return value
This routine returns the IP address of the interface used to send packets to host.
Location
The ip_mymach() routine is found in the following file:
inet\ip.c
ARM DUI 0144B |
Copyright © 1998-2001 ARM Limited. All rights reserved. |
10-7 |