| lh | 9ed821d | 2023-04-07 01:36:19 -0700 | [diff] [blame] | 1 | .\" |
| 2 | .\" Copyright 1998 by the Massachusetts Institute of Technology. |
| 3 | .\" |
| 4 | .\" Permission to use, copy, modify, and distribute this |
| 5 | .\" software and its documentation for any purpose and without |
| 6 | .\" fee is hereby granted, provided that the above copyright |
| 7 | .\" notice appear in all copies and that both that copyright |
| 8 | .\" notice and this permission notice appear in supporting |
| 9 | .\" documentation, and that the name of M.I.T. not be used in |
| 10 | .\" advertising or publicity pertaining to distribution of the |
| 11 | .\" software without specific, written prior permission. |
| 12 | .\" M.I.T. makes no representations about the suitability of |
| 13 | .\" this software for any purpose. It is provided "as is" |
| 14 | .\" without express or implied warranty. |
| 15 | .\" |
| 16 | .TH ARES_GETHOSTBYADDR 3 "24 July 1998" |
| 17 | .SH NAME |
| 18 | ares_gethostbyaddr \- Initiate a host query by address |
| 19 | .SH SYNOPSIS |
| 20 | .nf |
| 21 | .B #include <ares.h> |
| 22 | .PP |
| 23 | .B typedef void (*ares_host_callback)(void *\fIarg\fP, int \fIstatus\fP, |
| 24 | .B int \fItimeouts\fP, struct hostent *\fIhostent\fP) |
| 25 | .PP |
| 26 | .B void ares_gethostbyaddr(ares_channel \fIchannel\fP, const void *\fIaddr\fP, |
| 27 | .B int \fIaddrlen\fP, int \fIfamily\fP, ares_host_callback \fIcallback\fP, |
| 28 | .B void *\fIarg\fP) |
| 29 | .fi |
| 30 | .SH DESCRIPTION |
| 31 | The |
| 32 | .B ares_gethostbyaddr |
| 33 | function initiates a host query by address on the name service channel |
| 34 | identified by |
| 35 | .IR channel . |
| 36 | The parameters |
| 37 | .I addr |
| 38 | and |
| 39 | .I addrlen |
| 40 | give the address as a series of bytes, and |
| 41 | .I family |
| 42 | gives the type of address. When the query is complete or has failed, the ares |
| 43 | library will invoke \fIcallback\fP. Completion or failure of the query may |
| 44 | happen immediately, or may happen during a later call to |
| 45 | \fIares_process(3)\fP, \fIares_destroy(3)\fP or \fIares_cancel(3)\fP. |
| 46 | .PP |
| 47 | The callback argument |
| 48 | .I arg |
| 49 | is copied from the |
| 50 | .B ares_gethostbyaddr |
| 51 | argument |
| 52 | .IR arg . |
| 53 | The callback argument |
| 54 | .I status |
| 55 | indicates whether the query succeeded and, if not, how it failed. It |
| 56 | may have any of the following values: |
| 57 | .TP 19 |
| 58 | .B ARES_SUCCESS |
| 59 | The host lookup completed successfully. |
| 60 | .TP 19 |
| 61 | .B ARES_ENOTIMP |
| 62 | The ares library does not know how to look up addresses of type |
| 63 | .IR family . |
| 64 | .TP 19 |
| 65 | .B ARES_ENOTFOUND |
| 66 | The address |
| 67 | .I addr |
| 68 | was not found. |
| 69 | .TP 19 |
| 70 | .B ARES_ENOMEM |
| 71 | Memory was exhausted. |
| 72 | .TP 19 |
| 73 | .B ARES_ECANCELLED |
| 74 | The query was cancelled. |
| 75 | .TP 19 |
| 76 | .B ARES_EDESTRUCTION |
| 77 | The name service channel |
| 78 | .I channel |
| 79 | is being destroyed; the query will not be completed. |
| 80 | .PP |
| 81 | The callback argument |
| 82 | .I timeouts |
| 83 | reports how many times a query timed out during the execution of the |
| 84 | given request. |
| 85 | .PP |
| 86 | On successful completion of the query, the callback argument |
| 87 | .I hostent |
| 88 | points to a |
| 89 | .B struct hostent |
| 90 | containing the name of the host returned by the query. The callback |
| 91 | need not and should not attempt to free the memory pointed to by |
| 92 | .IR hostent ; |
| 93 | the ares library will free it when the callback returns. If the query |
| 94 | did not complete successfully, |
| 95 | .I hostent |
| 96 | will be |
| 97 | .BR NULL . |
| 98 | .SH SEE ALSO |
| 99 | .BR ares_process (3), |
| 100 | .BR ares_gethostbyname (3) |
| 101 | .SH AUTHOR |
| 102 | Greg Hudson, MIT Information Systems |
| 103 | .br |
| 104 | Copyright 1998 by the Massachusetts Institute of Technology. |