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/**************************************************************************/
/* */
/* Copyright (c) Microsoft Corporation. All rights reserved. */
/* */
/* This software is licensed under the Microsoft Software License */
/* Terms for Microsoft Azure RTOS. Full text of the license can be */
/* found in the LICENSE file at https://aka.ms/AzureRTOS_EULA */
/* and in the root directory of this software. */
/* */
/**************************************************************************/
/**************************************************************************/
/**************************************************************************/
/** */
/** NetX Component */
/** */
/** Internet Protocol (IP) */
/** */
/**************************************************************************/
/**************************************************************************/
#define NX_SOURCE_CODE
/* Include necessary system files. */
#include "nx_api.h"
#include "nx_ip.h"
#include "nx_packet.h"
#ifndef NX_DISABLE_IPV4
/**************************************************************************/
/* */
/* FUNCTION RELEASE */
/* */
/* _nx_ip_forward_packet_process PORTABLE C */
/* 6.1 */
/* AUTHOR */
/* */
/* Yuxin Zhou, Microsoft Corporation */
/* */
/* DESCRIPTION */
/* */
/* This function attempts to forward the IP packet to the destination */
/* IP by using the NetX send packet routine. Note that the IP header */
/* is still intact prior to the packet. */
/* */
/* INPUT */
/* */
/* ip_ptr Pointer to IP control block */
/* packet_ptr Pointer to packet to forward */
/* */
/* OUTPUT */
/* */
/* None */
/* */
/* CALLS */
/* */
/* _nx_packet_release Packet release */
/* _nx_packet_data_adjust Adjust the packet data to fill*/
/* the specified header */
/* _nx_ip_driver_packet_send Send the IP packet */
/* _nx_ip_fragment_forward_packet Fragment the forward packet */
/* _nx_ip_packet_deferred_receive IP deferred receive packet */
/* processing */
/* _nx_ip_route_find Find suitable outgoing */
/* interface */
/* */
/* CALLED BY */
/* */
/* _nx_ip_packet_receive Receive IP packet */
/* */
/* RELEASE HISTORY */
/* */
/* DATE NAME DESCRIPTION */
/* */
/* 05-19-2020 Yuxin Zhou Initial Version 6.0 */
/* 09-30-2020 Yuxin Zhou Modified comment(s), */
/* resulting in version 6.1 */
/* */
/**************************************************************************/
VOID _nx_ip_forward_packet_process(NX_IP *ip_ptr, NX_PACKET *packet_ptr)
{
NX_IPV4_HEADER *ip_header_ptr;
NX_INTERFACE *outgoing_interface = NX_NULL;
ULONG next_hop_address = 0;
ULONG destination_ip;
ULONG time_to_live;
ULONG fragment_bit;
ULONG status;
#ifdef NX_ENABLE_INTERFACE_CAPABILITY
UINT compute_checksum = 1;
#endif
ULONG checksum;
ULONG old_m;
ULONG new_m;
/* The NetX IP forwarding consists of simply sending the same packet out through
the internal send routine. Applications may choose to modify this code or
replace the nx_ip_forward_packet_process pointer in the IP structure to point
at an application-specific routine for forwarding. */
/* It's assumed that the IP header is still present in front of the packet. Position
backwards to access it. */
/*lint -e{927} -e{826} suppress cast of pointer to pointer, since it is necessary */
ip_header_ptr = (NX_IPV4_HEADER *)packet_ptr -> nx_packet_prepend_ptr;
/* Check for if the destination address is Class D address. */
if ((ip_header_ptr -> nx_ip_header_destination_ip & NX_IP_CLASS_D_MASK) == NX_IP_CLASS_D_TYPE)
{
/* Discard the packet. */
_nx_packet_release(packet_ptr);
return;
}
/* Determine if source address or destination addrss is link-local address(169.254/16 Hexadecimal:0xA9FE0000). */
if (((ip_header_ptr -> nx_ip_header_source_ip & 0xFFFF0000) == 0xA9FE0000) ||
((ip_header_ptr -> nx_ip_header_destination_ip & 0xFFFF0000) == 0xA9FE0000))
{
/* Discard the packet. */
_nx_packet_release(packet_ptr);
return;
}
/* Check whether find the correct forwarding interface. */
if (_nx_ip_route_find(ip_ptr, ip_header_ptr -> nx_ip_header_destination_ip, &outgoing_interface, &next_hop_address) == NX_SUCCESS)
{
/* If the forwarding interface is same as the receiving interface,
According to the RFC 792 Redirect Message on page 12,
send a redirect message to source address. */
/* Update the forwarding interface. */
/*lint -e{644} suppress variable might not be initialized, since "outgoing_interface" was initialized as long as return value is NX_SUCCESS. */
packet_ptr -> nx_packet_ip_interface = outgoing_interface;
/* Get the relevant information from original packet. */
destination_ip = ip_header_ptr -> nx_ip_header_destination_ip;
time_to_live = ((ip_header_ptr -> nx_ip_header_word_2 & NX_IP_TIME_TO_LIVE_MASK) >> NX_IP_TIME_TO_LIVE_SHIFT) - 1;
fragment_bit = (ip_header_ptr -> nx_ip_header_word_1 & NX_DONT_FRAGMENT);
/* If the TTL is 0, discard the packet. */
if (!time_to_live)
{
#ifndef NX_DISABLE_IP_INFO
/* Increment the IP receive packets dropped count. */
ip_ptr -> nx_ip_receive_packets_dropped++;
#endif
/* No correct forwarding interface, toss the packet! */
_nx_packet_release(packet_ptr);
return;
}
/* Update the TTL value. */
ip_header_ptr -> nx_ip_header_word_2 = (ip_header_ptr -> nx_ip_header_word_2 - 0x01000000);
/* Update the checksum, according to the RFC1624 page2, Eqn.3.
HC - old checksum in header
HC' - new checksum in header
m - old value of a 16-bit field
m' - new value of a 16-bit field
HC' = ~(C + (-m) + m')
= ~(~HC + ~m + m') */
#ifdef NX_ENABLE_INTERFACE_CAPABILITY
if (packet_ptr -> nx_packet_ip_interface -> nx_interface_capability_flag & NX_INTERFACE_CAPABILITY_IPV4_TX_CHECKSUM)
{
compute_checksum = 0;
}
#endif
#ifdef NX_ENABLE_INTERFACE_CAPABILITY
/* Check whether the destination IP address matched with one interface of IP instance. */
/*lint -e{613} suppress possible use of null pointer, since "outgoing_interface" was set in _nx_ip_route_find. */
if (outgoing_interface -> nx_interface_ip_address == destination_ip)
{
/* Clear the capability flag. */
packet_ptr -> nx_packet_interface_capability_flag &= (ULONG)(~NX_INTERFACE_CAPABILITY_IPV4_RX_CHECKSUM);
/* Set the computer checksum flag. */
compute_checksum = 1;
}
#endif
#ifdef NX_ENABLE_INTERFACE_CAPABILITY
/* Computer the checksum. */
/*lint -e{774} suppress boolean always evaluates to True, since it is necessary with NX_ENABLE_INTERFACE_CAPABILITY macro. */
if (compute_checksum)
{
#endif
/* Get the old checksum (HC) in header. */
checksum = ip_header_ptr -> nx_ip_header_word_2 & NX_LOWER_16_MASK;
/* Get the new TTL(m') in the header. */
new_m = (ip_header_ptr -> nx_ip_header_word_2 & 0xFFFF0000) >> 16;
/* Get the old TTL(m). */
old_m = new_m + 0x0100;
/* Update the checksum, get the new checksum(HC'),
The new_m is ULONG value, so need get the lower value after invert. */
checksum = ((~checksum) & 0xFFFF) + ((~old_m) & 0xFFFF) + new_m;
/* Fold a 4-byte value into a two byte value */
checksum = (checksum >> 16) + (checksum & 0xFFFF);
/* Do it again in case previous operation generates an overflow */
checksum = (checksum >> 16) + (checksum & 0xFFFF);
/* Now store the new checksum in the IP header. */
ip_header_ptr -> nx_ip_header_word_2 = ((ip_header_ptr -> nx_ip_header_word_2 & 0xFFFF0000) | ((~checksum) & NX_LOWER_16_MASK));
#ifdef NX_ENABLE_INTERFACE_CAPABILITY
}
else
{
/* Set the checksum to 0. */
ip_header_ptr -> nx_ip_header_word_2 = (ip_header_ptr -> nx_ip_header_word_2 & 0xFFFF0000);
packet_ptr -> nx_packet_interface_capability_flag |= NX_INTERFACE_CAPABILITY_IPV4_TX_CHECKSUM;
}
#endif /* NX_ENABLE_INTERFACE_CAPABILITY */
/* Endian swapping logic. If NX_LITTLE_ENDIAN is specified, these macros will
swap the endian of the IP header. */
NX_CHANGE_ULONG_ENDIAN(ip_header_ptr -> nx_ip_header_word_0);
NX_CHANGE_ULONG_ENDIAN(ip_header_ptr -> nx_ip_header_word_1);
NX_CHANGE_ULONG_ENDIAN(ip_header_ptr -> nx_ip_header_word_2);
NX_CHANGE_ULONG_ENDIAN(ip_header_ptr -> nx_ip_header_source_ip);
NX_CHANGE_ULONG_ENDIAN(ip_header_ptr -> nx_ip_header_destination_ip);
/* Check whether the destination IP address matched with one interface of IP instance. */
/*lint -e{613} suppress possible use of null pointer, since "outgoing_interface" was set in _nx_ip_route_find. */
if (outgoing_interface -> nx_interface_ip_address == destination_ip)
{
/* Forward this packet to correct interface. */
_nx_ip_packet_deferred_receive(ip_ptr, packet_ptr);
return;
}
else
{
/* Check if the packet can fill physical header. */
status = _nx_packet_data_adjust(packet_ptr, NX_PHYSICAL_HEADER);
/* Check status. */
if (status)
{
/* Release the packet. */
_nx_packet_release(packet_ptr);
return;
}
/* Determine if fragmentation is needed. */
if (packet_ptr -> nx_packet_length <= packet_ptr -> nx_packet_address.nx_packet_interface_ptr -> nx_interface_ip_mtu_size)
{
/* Call the function to directly forward the packet. */
/*lint -e{644} suppress variable might not be initialized, since "next_hop_address" was initialized in _nx_ip_route_find. */
_nx_ip_driver_packet_send(ip_ptr, packet_ptr, destination_ip, fragment_bit, next_hop_address);
return;
}
#ifndef NX_DISABLE_FRAGMENTATION
else
{
/* Check the DF bit flag. */
if ((ip_ptr -> nx_ip_fragment_processing) && (!(fragment_bit & NX_DONT_FRAGMENT)))
{
/* Fragment and send the packet. */
_nx_ip_fragment_forward_packet(ip_ptr, packet_ptr, destination_ip, NX_FRAGMENT_OKAY, next_hop_address);
return;
}
}
#endif
}
}
/* No correct forwarding interface, toss the packet! */
_nx_packet_release(packet_ptr);
return;
}
#endif /* NX_DISABLE_IPV4 */