08-21-2008
From
UDP: the User Datagram Protocol
Quote:
Although UDP provides error checking, it does not do anything to recover from an error. Some implementations of UDP simply discard the damaged segment; others pass the damaged segment to the application with a warning.
So getting the checksum is OS and IP-stack implementation-dependent. BTW: How are you dealing with missing packets? (you are tracking sequence numbers, yes?)
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LEARN ABOUT FREEBSD
udplite
UDPLITE(4) BSD Kernel Interfaces Manual UDPLITE(4)
NAME
udplite -- Lightweight User Datagram Protocol
SYNOPSIS
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/udplite.h>
int
socket(AF_INET, SOCK_DGRAM, IPPROTO_UDPLITE);
DESCRIPTION
The UDP-Lite protocol provides a partial checksum which allows corrupted packets to be transmitted to the receiving application. This has
advantages for some types of multimedia transport that may be able to make use of slightly damaged datagrams, rather than having them dis-
carded by lower-layer protocols.
UDP-Lite supports a number of socket options which can be set with setsockopt(2) and tested with getsockopt(2):
UDPLITE_SEND_CSCOV This option sets the sender checksum coverage. A value of zero indicates that all sent packets will have full checksum
coverage. A value of 8 to 65535 limits the checksum coverage of all sent packets to the value given.
UDPLITE_RECV_CSCOV This option is the receiver-side analogue. A value of zero instructs the kernel to drop all received packets not having
full checksum coverage. A value of 8 to 65535 instructs the kernel to drop all received packets with a partial checksum
coverage smaller than the value specified.
ERRORS
A socket operation may fail with one of the following errors returned:
[EISCONN] when trying to establish a connection on a socket which already has one, or when trying to send a datagram with the desti-
nation address specified and the socket is already connected;
[ENOTCONN] when trying to send a datagram, but no destination address is specified, and the socket has not been connected;
[ENOBUFS] when the system runs out of memory for an internal data structure;
[EADDRINUSE] when an attempt is made to create a socket with a port which has already been allocated;
[EADDRNOTAVAIL] when an attempt is made to create a socket with a network address for which no network interface exists.
SEE ALSO
getsockopt(2), recv(2), send(2), socket(2)
BSD
October 1, 2014 BSD