From d95f3dc0b117b0677700dae8dd51145c9b6f2d08 Mon Sep 17 00:00:00 2001 From: Rick Deist Date: Sat, 17 Mar 2018 20:10:04 +0100 Subject: resolve: add CURLOPT_DNS_SHUFFLE_ADDRESSES This patch adds CURLOPT_DNS_SHUFFLE_ADDRESSES to explicitly request shuffling of IP addresses returned for a hostname when there is more than one. This is useful when the application knows that a round robin approach is appropriate and is willing to accept the consequences of potentially discarding some preference order returned by the system's implementation. Closes #1694 --- docs/libcurl/curl_easy_setopt.3 | 2 + docs/libcurl/opts/CURLOPT_DNS_SHUFFLE_ADDRESSES.3 | 69 +++++++++++++++++++++ docs/libcurl/opts/Makefile.inc | 1 + docs/libcurl/symbols-in-versions | 1 + include/curl/curl.h | 3 + lib/hostip.c | 74 ++++++++++++++++++++++- lib/hostip.h | 13 +++- lib/setopt.c | 3 + lib/urldata.h | 2 + packages/OS400/curl.inc.in | 2 + tests/data/Makefile.inc | 1 + tests/data/test1608 | 26 ++++++++ tests/unit/Makefile.inc | 6 +- tests/unit/unit1608.c | 70 +++++++++++++++++++++ 14 files changed, 270 insertions(+), 3 deletions(-) create mode 100644 docs/libcurl/opts/CURLOPT_DNS_SHUFFLE_ADDRESSES.3 create mode 100644 tests/data/test1608 create mode 100644 tests/unit/unit1608.c diff --git a/docs/libcurl/curl_easy_setopt.3 b/docs/libcurl/curl_easy_setopt.3 index b7d67f360..97883d85d 100644 --- a/docs/libcurl/curl_easy_setopt.3 +++ b/docs/libcurl/curl_easy_setopt.3 @@ -468,6 +468,8 @@ Bind name resolves to this IP4 address. See \fICURLOPT_DNS_LOCAL_IP4(3)\fP Bind name resolves to this IP6 address. See \fICURLOPT_DNS_LOCAL_IP6(3)\fP .IP CURLOPT_DNS_SERVERS Preferred DNS servers. See \fICURLOPT_DNS_SERVERS(3)\fP +.IP CURLOPT_DNS_SHUFFLE_ADDRESSES +Shuffle addresses before use. See \fICURLOPT_DNS_SHUFFLE_ADDRESSES(3)\fP .IP CURLOPT_ACCEPTTIMEOUT_MS Timeout for waiting for the server's connect back to be accepted. See \fICURLOPT_ACCEPTTIMEOUT_MS(3)\fP .IP CURLOPT_HAPPY_EYEBALLS_TIMEOUT_MS diff --git a/docs/libcurl/opts/CURLOPT_DNS_SHUFFLE_ADDRESSES.3 b/docs/libcurl/opts/CURLOPT_DNS_SHUFFLE_ADDRESSES.3 new file mode 100644 index 000000000..8af2d0aa2 --- /dev/null +++ b/docs/libcurl/opts/CURLOPT_DNS_SHUFFLE_ADDRESSES.3 @@ -0,0 +1,69 @@ +.\" ************************************************************************** +.\" * _ _ ____ _ +.\" * Project ___| | | | _ \| | +.\" * / __| | | | |_) | | +.\" * | (__| |_| | _ <| |___ +.\" * \___|\___/|_| \_\_____| +.\" * +.\" * Copyright (C) 1998 - 2018, Daniel Stenberg, , et al. +.\" * +.\" * This software is licensed as described in the file COPYING, which +.\" * you should have received as part of this distribution. The terms +.\" * are also available at https://curl.haxx.se/docs/copyright.html. +.\" * +.\" * You may opt to use, copy, modify, merge, publish, distribute and/or sell +.\" * copies of the Software, and permit persons to whom the Software is +.\" * furnished to do so, under the terms of the COPYING file. +.\" * +.\" * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY +.\" * KIND, either express or implied. +.\" * +.\" ************************************************************************** +.\" +.TH CURLOPT_DNS_SHUFFLE_ADDRESSES 3 "3 March 2018" "libcurl 7.60.0" "curl_easy_setopt options" +.SH NAME +CURLOPT_DNS_SHUFFLE_ADDRESSES \- Shuffle addresses when a hostname returns more than one +.SH SYNOPSIS +.nf +#include + +CURLcode curl_easy_setopt(CURL *handle, CURLOPT_DNS_SHUFFLE_ADDRESSES, long onoff); +.fi +.SH DESCRIPTION +When a name is resolved and more than one IP address is returned, shuffle the +order of all returned addresses so that they will be used in a random order. +This is similar to the ordering behavior of gethostbyname which is no longer +used on most platforms. + +Addresses will not be reshuffled if a name resolution is completed using the +DNS cache. \fICURLOPT_DNS_CACHE_TIMEOUT(3)\fP can be used together with this +option to reduce DNS cache timeout or disable caching entirely if frequent +reshuffling is needed. + +Since the addresses returned will be reordered randomly, their order will not +be in accordance with RFC 3484 or any other deterministic order that may be +generated by the system's name resolution implementation. This may have +performance impacts and may cause IPv4 to be used before IPv6 or vice versa. +.SH DEFAULT +0 (disabled) +.SH PROTOCOLS +All +.SH EXAMPLE +.nf +CURL *curl = curl_easy_init(); +if(curl) { + curl_easy_setopt(curl, CURLOPT_URL, "https://example.com"); + curl_easy_setopt(curl, CURLOPT_DNS_SHUFFLE_ADDRESSES, 1L); + + curl_easy_perform(curl); + + /* always cleanup */ + curl_easy_cleanup(curl); +} +.fi +.SH AVAILABILITY +Added in 7.60.0 +.SH RETURN VALUE +CURLE_OK or an error such as CURLE_UNKNOWN_OPTION. +.SH "SEE ALSO" +.BR CURLOPT_DNS_CACHE_TIMEOUT "(3), " CURLOPT_IPRESOLVE "(3), " diff --git a/docs/libcurl/opts/Makefile.inc b/docs/libcurl/opts/Makefile.inc index b370082d6..80488bfa3 100644 --- a/docs/libcurl/opts/Makefile.inc +++ b/docs/libcurl/opts/Makefile.inc @@ -112,6 +112,7 @@ man_MANS = \ CURLOPT_DNS_LOCAL_IP4.3 \ CURLOPT_DNS_LOCAL_IP6.3 \ CURLOPT_DNS_SERVERS.3 \ + CURLOPT_DNS_SHUFFLE_ADDRESSES.3 \ CURLOPT_DNS_USE_GLOBAL_CACHE.3 \ CURLOPT_EGDSOCKET.3 \ CURLOPT_ERRORBUFFER.3 \ diff --git a/docs/libcurl/symbols-in-versions b/docs/libcurl/symbols-in-versions index 2877de7f1..52e8407dd 100644 --- a/docs/libcurl/symbols-in-versions +++ b/docs/libcurl/symbols-in-versions @@ -373,6 +373,7 @@ CURLOPT_DNS_INTERFACE 7.33.0 CURLOPT_DNS_LOCAL_IP4 7.33.0 CURLOPT_DNS_LOCAL_IP6 7.33.0 CURLOPT_DNS_SERVERS 7.24.0 +CURLOPT_DNS_SHUFFLE_ADDRESSES 7.60.0 CURLOPT_DNS_USE_GLOBAL_CACHE 7.9.3 7.11.1 CURLOPT_EGDSOCKET 7.7 CURLOPT_ENCODING 7.10 diff --git a/include/curl/curl.h b/include/curl/curl.h index 43d5e031f..3fd4ca87d 100644 --- a/include/curl/curl.h +++ b/include/curl/curl.h @@ -1844,6 +1844,9 @@ typedef enum { /* send HAProxy PROXY protocol header? */ CINIT(HAPROXYPROTOCOL, LONG, 274), + /* shuffle addresses before use when DNS returns multiple */ + CINIT(DNS_SHUFFLE_ADDRESSES, LONG, 275), + CURLOPT_LASTENTRY /* the last unused */ } CURLoption; diff --git a/lib/hostip.c b/lib/hostip.c index 8554d39d1..c2f9defd9 100644 --- a/lib/hostip.c +++ b/lib/hostip.c @@ -5,7 +5,7 @@ * | (__| |_| | _ <| |___ * \___|\___/|_| \_\_____| * - * Copyright (C) 1998 - 2017, Daniel Stenberg, , et al. + * Copyright (C) 1998 - 2018, Daniel Stenberg, , et al. * * This software is licensed as described in the file COPYING, which * you should have received as part of this distribution. The terms @@ -54,6 +54,7 @@ #include "sendf.h" #include "hostip.h" #include "hash.h" +#include "rand.h" #include "share.h" #include "strerror.h" #include "url.h" @@ -366,6 +367,70 @@ Curl_fetch_addr(struct connectdata *conn, return dns; } +/* + * Curl_shuffle_addr() shuffles the order of addresses in a 'Curl_addrinfo' + * struct by re-linking its linked list. + * + * The addr argument should be the address of a pointer to the head node of a + * `Curl_addrinfo` list and it will be modified to point to the new head after + * shuffling. + * + * Not declared static only to make it easy to use in a unit test! + * + * @unittest: 1608 + */ +CURLcode Curl_shuffle_addr(struct Curl_easy *data, Curl_addrinfo **addr) +{ + CURLcode result = CURLE_OK; + const int num_addrs = Curl_num_addresses(*addr); + + if(num_addrs > 1) { + Curl_addrinfo **nodes; + infof(data, "Shuffling %i addresses", num_addrs); + + nodes = malloc(num_addrs*sizeof(*nodes)); + if(nodes) { + int i; + unsigned int *rnd; + const size_t rnd_size = num_addrs * sizeof(*rnd); + + /* build a plain array of Curl_addrinfo pointers */ + nodes[0] = *addr; + for(i = 1; i < num_addrs; i++) { + nodes[i] = nodes[i-1]->ai_next; + } + + rnd = malloc(rnd_size); + if(rnd) { + /* Fisher-Yates shuffle */ + if(Curl_rand(data, (unsigned char *)rnd, rnd_size) == CURLE_OK) { + Curl_addrinfo *swap_tmp; + for(i = num_addrs - 1; i > 0; i--) { + swap_tmp = nodes[rnd[i] % (i + 1)]; + nodes[rnd[i] % (i + 1)] = nodes[i]; + nodes[i] = swap_tmp; + } + + /* relink list in the new order */ + for(i = 1; i < num_addrs; i++) { + nodes[i-1]->ai_next = nodes[i]; + } + + nodes[num_addrs-1]->ai_next = NULL; + *addr = nodes[0]; + } + free(rnd); + } + else + result = CURLE_OUT_OF_MEMORY; + free(nodes); + } + else + result = CURLE_OUT_OF_MEMORY; + } + return result; +} + /* * Curl_cache_addr() stores a 'Curl_addrinfo' struct in the DNS cache. * @@ -386,6 +451,13 @@ Curl_cache_addr(struct Curl_easy *data, struct Curl_dns_entry *dns; struct Curl_dns_entry *dns2; + /* shuffle addresses if requested */ + if(data->set.dns_shuffle_addresses) { + CURLcode result = Curl_shuffle_addr(data, &addr); + if(!result) + return NULL; + } + /* Create an entry id, based upon the hostname and port */ entry_id = create_hostcache_id(hostname, port); /* If we can't create the entry id, fail */ diff --git a/lib/hostip.h b/lib/hostip.h index 298eeeee3..1de4bee8d 100644 --- a/lib/hostip.h +++ b/lib/hostip.h @@ -7,7 +7,7 @@ * | (__| |_| | _ <| |___ * \___|\___/|_| \_\_____| * - * Copyright (C) 1998 - 2017, Daniel Stenberg, , et al. + * Copyright (C) 1998 - 2018, Daniel Stenberg, , et al. * * This software is licensed as described in the file COPYING, which * you should have received as part of this distribution. The terms @@ -182,6 +182,17 @@ struct Curl_dns_entry * Curl_fetch_addr(struct connectdata *conn, const char *hostname, int port); + +/* + * Curl_shuffle_addr() shuffles the order of addresses in a 'Curl_addrinfo' + * struct by re-linking its linked list. + * + * The addr argument should be the address of a pointer to the head node of a + * `Curl_addrinfo` list and it will be modified to point to the new head after + * shuffling. + */ +CURLcode Curl_shuffle_addr(struct Curl_easy *data, Curl_addrinfo **addr); + /* * Curl_cache_addr() stores a 'Curl_addrinfo' struct in the DNS cache. * diff --git a/lib/setopt.c b/lib/setopt.c index 737a60f85..da364fa81 100644 --- a/lib/setopt.c +++ b/lib/setopt.c @@ -2561,6 +2561,9 @@ CURLcode Curl_vsetopt(struct Curl_easy *data, CURLoption option, return CURLE_BAD_FUNCTION_ARGUMENT; data->set.happy_eyeballs_timeout = arg; break; + case CURLOPT_DNS_SHUFFLE_ADDRESSES: + data->set.dns_shuffle_addresses = (0 != va_arg(param, long)) ? TRUE:FALSE; + break; default: /* unknown tag and its companion, just ignore: */ result = CURLE_UNKNOWN_OPTION; diff --git a/lib/urldata.h b/lib/urldata.h index dad31cd4e..35bbb8590 100644 --- a/lib/urldata.h +++ b/lib/urldata.h @@ -1674,6 +1674,8 @@ struct UserDefined { bool suppress_connect_headers; /* suppress proxy CONNECT response headers from user callbacks */ + bool dns_shuffle_addresses; /* whether to shuffle addresses before use */ + struct Curl_easy *stream_depends_on; bool stream_depends_e; /* set or don't set the Exclusive bit */ int stream_weight; diff --git a/packages/OS400/curl.inc.in b/packages/OS400/curl.inc.in index a21ee9bba..ac302967f 100644 --- a/packages/OS400/curl.inc.in +++ b/packages/OS400/curl.inc.in @@ -1330,6 +1330,8 @@ d c 20272 d CURLOPT_RESOLVER_START_DATA... d c 10273 + d CURLOPT_DNS_SHUFFLE_ADDRESSES... + d c 00274 * /if not defined(CURL_NO_OLDIES) d CURLOPT_FILE c 10001 diff --git a/tests/data/Makefile.inc b/tests/data/Makefile.inc index ca0c7edd1..2f5721318 100644 --- a/tests/data/Makefile.inc +++ b/tests/data/Makefile.inc @@ -177,6 +177,7 @@ test1533 test1534 test1535 test1536 test1537 test1538 \ test1540 \ test1550 test1551 test1552 test1553 test1554 test1555 test1556 \ test1600 test1601 test1602 test1603 test1604 test1605 test1606 test1607 \ +test1608 \ \ test1700 test1701 test1702 \ \ diff --git a/tests/data/test1608 b/tests/data/test1608 new file mode 100644 index 000000000..702310757 --- /dev/null +++ b/tests/data/test1608 @@ -0,0 +1,26 @@ + + + +unittest +curlopt_dns_shuffle_addresses + + + +# +# Client-side + + +none + + +unittest + + +verify DNS shuffling + + +unit1608 + + + + diff --git a/tests/unit/Makefile.inc b/tests/unit/Makefile.inc index 9a19f51d1..f77da7588 100644 --- a/tests/unit/Makefile.inc +++ b/tests/unit/Makefile.inc @@ -9,7 +9,8 @@ UNITPROGS = unit1300 unit1301 unit1302 unit1303 unit1304 unit1305 unit1307 \ unit1308 unit1309 unit1323 \ unit1330 unit1394 unit1395 unit1396 unit1397 unit1398 \ unit1399 \ - unit1600 unit1601 unit1602 unit1603 unit1604 unit1605 unit1606 unit1607 + unit1600 unit1601 unit1602 unit1603 unit1604 unit1605 unit1606 unit1607 \ + unit1608 unit1300_SOURCES = unit1300.c $(UNITFILES) unit1300_CPPFLAGS = $(AM_CPPFLAGS) @@ -88,3 +89,6 @@ unit1606_CPPFLAGS = $(AM_CPPFLAGS) unit1607_SOURCES = unit1607.c $(UNITFILES) unit1607_CPPFLAGS = $(AM_CPPFLAGS) + +unit1608_SOURCES = unit1608.c $(UNITFILES) +unit1608_CPPFLAGS = $(AM_CPPFLAGS) diff --git a/tests/unit/unit1608.c b/tests/unit/unit1608.c new file mode 100644 index 000000000..9ae474ba9 --- /dev/null +++ b/tests/unit/unit1608.c @@ -0,0 +1,70 @@ +/*************************************************************************** + * _ _ ____ _ + * Project ___| | | | _ \| | + * / __| | | | |_) | | + * | (__| |_| | _ <| |___ + * \___|\___/|_| \_\_____| + * + * Copyright (C) 1998 - 2018, Daniel Stenberg, , et al. + * + * This software is licensed as described in the file COPYING, which + * you should have received as part of this distribution. The terms + * are also available at https://curl.haxx.se/docs/copyright.html. + * + * You may opt to use, copy, modify, merge, publish, distribute and/or sell + * copies of the Software, and permit persons to whom the Software is + * furnished to do so, under the terms of the COPYING file. + * + * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY + * KIND, either express or implied. + * + ***************************************************************************/ +#include "curlcheck.h" + +#include "hostip.h" + +#define NUM_ADDRS 8 +static struct Curl_addrinfo addrs[NUM_ADDRS]; + +static CURLcode unit_setup(void) +{ + int i; + for(i = 0; i < NUM_ADDRS - 1; i++) { + addrs[i].ai_next = &addrs[i + 1]; + } + + return CURLE_OK; +} + +static void unit_stop(void) +{ + +} + +UNITTEST_START +{ + int i; + CURLcode code; + struct Curl_addrinfo* addrhead = addrs; + + struct Curl_easy *easy = curl_easy_init(); + abort_unless(easy, "out of memory"); + + code = curl_easy_setopt(easy, CURLOPT_DNS_SHUFFLE_ADDRESSES, 1L); + abort_unless(code == CURLE_OK, "curl_easy_setopt failed"); + + /* Shuffle repeatedly and make sure that the list changes */ + for(i = 0; i < 10; i++) { + if(CURLE_OK != Curl_shuffle_addr(easy, &addrhead)) + break; + if(addrhead != addrs) + break; + } + + curl_easy_cleanup(easy); + + abort_unless(addrhead != addrs, "addresses are not being reordered"); + + return 0; +} +UNITTEST_STOP -- cgit v1.2.3