Andrew Boyson / net

A stack which works with or without an Mbed os library. Provides IPv4 or IPv6 with a full 1500 byte buffer.

Dependents:   oldheating gps motorhome heating

udp/dns/dnslabel.h@200:5acbc41bf469, 2021-05-20 (annotated)

Committer:
andrewboyson
Date:
Thu May 20 14:32:52 2021 +0000
Revision:
200:5acbc41bf469
Parent:
183:ee809769bf89 
Increased number of arp entries from 20 to 30 to accommodate the number of WIZ devices plus a few incoming port 80 calls from the internet.

Who changed what in which revision?

UserRevisionLine numberNew contents of line
andrewboyson 128:79052cb4a41c 1 extern void DnsLabelCopy(char* dst, char* src);
andrewboyson 183:ee809769bf89 2 extern bool DnsLabelIsExternal(char* p);
andrewboyson 128:79052cb4a41c 3 extern bool DnsLabelIsSame(char* pA, char* pB);
andrewboyson 128:79052cb4a41c 4 extern int DnsLabelMakeFullNameFromName (int protocol, const char* name, int size, char* fqdn);
andrewboyson 128:79052cb4a41c 5 extern int DnsLabelStripNameFromFullName(int protocol, char* fqdn, int size, char* name);
andrewboyson 128:79052cb4a41c 6
andrewboyson 128:79052cb4a41c 7 #define DNS_MAX_LABEL_LENGTH 63
andrewboyson 128:79052cb4a41c 8
andrewboyson 128:79052cb4a41c 9 /*
andrewboyson 128:79052cb4a41c 10 rfc1035/rfc1123 label (DNS_LABEL):
andrewboyson 128:79052cb4a41c 11 An alphanumeric (a-z, and 0-9) string, with a maximum length of 63 characters,
andrewboyson 128:79052cb4a41c 12 with the '-' character allowed anywhere except the first or last character,
andrewboyson 128:79052cb4a41c 13 suitable for use as a hostname or segment in a domain name.
andrewboyson 128:79052cb4a41c 14
andrewboyson 128:79052cb4a41c 15 Labels are stored in DNS as <length><label>, length is a single byte
andrewboyson 128:79052cb4a41c 16 two high bits of the length field reserved for something else (compression) thus leaving 6 bits for the length itself
andrewboyson 128:79052cb4a41c 17 2^6=64 possible values - 0..63.
andrewboyson 128:79052cb4a41c 18
andrewboyson 128:79052cb4a41c 19 In our case reserve 64 bytes for all labels which leaves room for a terminating null
andrewboyson 128:79052cb4a41c 20 so always delare labels, hostnames or segments as [DNS_MAX_LABEL_LENGTH+1].
andrewboyson 128:79052cb4a41c 21 */