|UDPLITE(7)||Linux Programmer's Manual||UDPLITE(7)|
sockfd = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDPLITE);
UDP-Lite is an extension of UDP (RFC 768) to support variable-length checksums. This has advantages for some types of multimedia transport that may be able to make use of slightly damaged datagrams, rather than having them discarded by lower-layer protocols.
The variable-length checksum coverage is set via a setsockopt(2) option. If this option is not set, the only difference from UDP is in using a different IP protocol identifier (IANA number 136).
The UDP-Lite implementation is a full extension of udp(7)—that is, it shares the same API and API behavior, and in addition offers two socket options to control the checksum coverage.
The following two options are specific to UDP-Lite.
- This option sets the sender checksum coverage and takes an int as argument, with a checksum coverage value in the range 0..2^16-1.
- A value of 0 means that the entire datagram is always covered. Values from 1-7 are illegal (RFC 3828, 3.1) and are rounded up to the minimum coverage of 8.
- With regard to IPv6 jumbograms (RFC 2675), the UDP-Litev6 checksum coverage is limited to the first 2^16-1 octets, as per RFC 3828, 3.5. Higher values are therefore silently truncated to 2^16-1. If in doubt, the current coverage value can always be queried using getsockopt(2).
- This is the receiver-side analogue and uses the same argument format and value range as UDPLITE_SEND_CSCOV. This option is not required to enable traffic with partial checksum coverage. Its function is that of a traffic filter: when enabled, it instructs the kernel to drop all packets which have a coverage less than the specified coverage value.
- When the value of UDPLITE_RECV_CSCOV exceeds the actual packet coverage, incoming packets are silently dropped, but may generate a warning message in the system log.
- Basic UDP-Litev4 statistics counters.
- Basic UDP-Litev6 statistics counters.
#define IPPROTO_UDPLITE 136 #define UDPLITE_SEND_CSCOV 10 #define UDPLITE_RECV_CSCOV 11
RFC 3828 for the Lightweight User Datagram Protocol (UDP-Lite).
Documentation/networking/udplite.txt in the Linux kernel source tree