Annotation of libwww/Library/src/HTDNS.html, revision 2.13
2.1 frystyk 1: <HTML>
2: <HEAD>
2.13 ! frystyk 3: <!-- Changed by: Henrik Frystyk Nielsen, 2-Apr-1996 -->
! 4: <TITLE>W3C Reference Library libwww DNS Class</TITLE>
2.1 frystyk 5: </HEAD>
6: <BODY>
2.13 ! frystyk 7: <H1>
! 8: Domain Name Service Class
! 9: </H1>
2.1 frystyk 10: <PRE>
11: /*
12: ** (c) COPYRIGHT MIT 1995.
13: ** Please first read the full copyright statement in the file COPYRIGH.
14: */
15: </PRE>
2.13 ! frystyk 16: <P>
! 17: The DNS Class defines generic access to the DNS system. It maintains
! 18: a cache of all visited hosts so that subsequent connects to the same host
! 19: doesn't imply a new request to the DNS every time. Multihomed hosts are treated
! 20: specially in that the time spend on every connect is measured and kept in
! 21: the cache. On the next request to the same host, the IP-address with the
! 22: lowest average connect time is chosen. If one IP-address fails completely,
! 23: e.g. <EM>connection refused</EM> then it disabled and HTDoConnect tries one
! 24: of the other IP-addresses to the same host.
! 25: <P>
! 26: Every entry in the cache has its own time to live (TTL) and hence the cache
! 27: manages its own automatic garbage collection. Currently the TTL is <B>not</B>
! 28: bound to the DNS records which should be changed. You can set the DNS object
! 29: TTL
! 30: <P>
! 31: This module is implemented by <A HREF="HTDNS.c">HTDNS.c</A>, and it is a
! 32: part of the <A HREF="http://www.w3.org/pub/WWW/Library/"> W3C Reference
! 33: Library</A>.
2.1 frystyk 34: <PRE>
35: #ifndef HTDNS_H
36: #define HTDNS_H
2.13 ! frystyk 37:
2.1 frystyk 38: </PRE>
2.13 ! frystyk 39: <PRE>typedef struct _HTdns HTdns;
2.1 frystyk 40: </PRE>
2.13 ! frystyk 41: <H2>
! 42: DNS Cache Expiration Time
! 43: </H2>
! 44: <P>
2.12 frystyk 45: When to remove an entry in the cache. The default value is 12h.
2.1 frystyk 46: <PRE>
47: extern void HTDNS_setTimeout (time_t timeout);
48: extern time_t HTDNS_timeout (time_t timeout);
49: </PRE>
2.13 ! frystyk 50: <H2>
! 51: Creation and Deletion Methods
! 52: </H2>
! 53: <H3>
! 54: Add a DNS Object
! 55: </H3>
! 56: <P>
! 57: Add an element to the cache of visited hosts. The <CODE>homes</CODE> variable
! 58: indicates the number of IP addresses found when looking up the name. A host
! 59: name must <B>NOT</B> contain a port number.
! 60: <PRE>
! 61: extern HTdns * HTDNS_add (HTList * list, struct hostent * element,
! 62: char * host, int * homes);
! 63: </PRE>
! 64: <H3>
! 65: Delete a DNS object
! 66: </H3>
! 67: <P>
! 68: This function flushes the DNS object from the cache and frees up memory
2.1 frystyk 69: <PRE>
2.9 frystyk 70: extern BOOL HTDNS_delete (const char * host);
2.1 frystyk 71: </PRE>
2.13 ! frystyk 72: <H3>
! 73: Delete ALL DNS objects
! 74: </H3>
! 75: <P>
2.1 frystyk 76: This function is called from <A HREF="HTAccess.html#Library">
2.13 ! frystyk 77: HTLibTerminate</A>. It can be called at any point in time if the DNS cache
! 78: is going to be flushed.
2.1 frystyk 79: <PRE>
80: extern BOOL HTDNS_deleteAll (void);
81: </PRE>
2.13 ! frystyk 82: <H2>
! 83: DNS Class Methods
! 84: </H2>
! 85: <H3>
! 86: Recalculating the Time Weights on Multihomed Host
! 87: </H3>
! 88: <P>
! 89: On every connect to a multihomed host, the average connect time is updated
! 90: exponentially for all the entries.
! 91: <PRE>
! 92: extern BOOL HTDNS_updateWeigths (HTdns *dns, int cur, time_t deltatime);
! 93: </PRE>
! 94: <H2>
! 95: Resolver Functions
! 96: </H2>
! 97: <P>
! 98: These are the functions that resolve a host name
! 99: <H3>
! 100: Get Host By Socket
! 101: </H3>
! 102: <P>
! 103: This function should have been called HTGetHostByAddr but for historical
! 104: reasons this is not the case.
2.1 frystyk 105: <PRE>
2.7 frystyk 106: extern char * HTGetHostBySock (int soc);
2.1 frystyk 107: </PRE>
2.13 ! frystyk 108: <H3>
! 109: Get Host By Name
! 110: </H3>
! 111: <P>
! 112: This function gets the address of the host and puts it in to the socket
! 113: structure. It maintains its own cache of connections so that the communication
! 114: to the Domain Name Server is minimized. Returns the number of homes or -1
! 115: if error.
2.1 frystyk 116: <PRE>
117: extern int HTGetHostByName (struct _HTNet *net, char *host);
118: </PRE>
119: <PRE>
120: #endif
121: </PRE>
2.13 ! frystyk 122: <P>
! 123: <HR>
2.12 frystyk 124: <ADDRESS>
2.13 ! frystyk 125: @(#) $Id: HTDNS.html,v 2.12 1996/04/12 17:46:22 frystyk Exp $
2.12 frystyk 126: </ADDRESS>
2.13 ! frystyk 127: </BODY></HTML>
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