CURLOPT_RESOLVE: Add support for multiple IP addresses per entry

This enables users to preresolve but still take advantage of happy
eyeballs and trying multiple addresses if some are not connecting.

Ref: https://github.com/curl/curl/pull/2260

9 files changed, 347 insertions, 42 deletions

diff --git a/docs/cmdline-opts/resolve.d b/docs/cmdline-opts/resolve.d
index 91539b8e9..9e1457b5e 100644
--- a/docs/cmdline-opts/resolve.d
+++ b/docs/cmdline-opts/resolve.d
@@ -1,5 +1,5 @@
 Long: resolve
-Arg: <host:port:address>
+Arg: <host:port:address[,address]...>
 Help: Resolve the host+port to this address
 Added: 7.21.3
 ---
@@ -16,4 +16,6 @@ is set to make curl use another IP version.
 
 Support for providing the IP address within [brackets] was added in 7.57.0.
 
+Support for providing multiple IP addresses per entry was added in 7.59.0.
+
 This option can be used many times to add many host names to resolve.
diff --git a/docs/libcurl/opts/CURLOPT_RESOLVE.3 b/docs/libcurl/opts/CURLOPT_RESOLVE.3
index c22f7b006..b4d79cf3b 100644
--- a/docs/libcurl/opts/CURLOPT_RESOLVE.3
+++ b/docs/libcurl/opts/CURLOPT_RESOLVE.3
@@ -37,10 +37,12 @@ list of \fBstruct curl_slist\fP structs properly filled in. Use
 to clean up an entire list.
 
 Each single name resolve string should be written using the format
-HOST:PORT:ADDRESS where HOST is the name libcurl will try to resolve, PORT is
-the port number of the service where libcurl wants to connect to the HOST and
-ADDRESS is the numerical IP address. If libcurl is built to support IPv6,
-ADDRESS can of course be either IPv4 or IPv6 style addressing.
+HOST:PORT:ADDRESS[,ADDRESS]... where HOST is the name libcurl will try
+to resolve, PORT is the port number of the service where libcurl wants
+to connect to the HOST and ADDRESS is one or more numerical IP
+addresses. If you specify multiple ip addresses they need to be
+separated by comma. If libcurl is built to support IPv6, each of the
+ADDRESS entries can of course be either IPv4 or IPv6 style addressing.
 
 This option effectively pre-populates the DNS cache with entries for the
 host+port pair so redirects and everything that operations against the
@@ -57,6 +59,8 @@ by including a string in the linked list that uses the format
 and port number must exactly match what was already added previously.
 
 Support for providing the ADDRESS within [brackets] was added in 7.57.0.
+
+Support for providing multiple IP addresses per entry was added in 7.59.0.
 .SH DEFAULT
 NULL
 .SH PROTOCOLS
diff --git a/lib/connect.c b/lib/connect.c
index d56cf2f16..c3add43cc 100644
--- a/lib/connect.c
+++ b/lib/connect.c
@@ -619,8 +619,8 @@ void Curl_persistconninfo(struct connectdata *conn)
 
 /* retrieves ip address and port from a sockaddr structure.
    note it calls Curl_inet_ntop which sets errno on fail, not SOCKERRNO. */
-static bool getaddressinfo(struct sockaddr *sa, char *addr,
-                           long *port)
+bool Curl_getaddressinfo(struct sockaddr *sa, char *addr,
+                         long *port)
 {
   unsigned short us_port;
   struct sockaddr_in *si = NULL;
@@ -700,16 +700,16 @@ void Curl_updateconninfo(struct connectdata *conn, curl_socket_t sockfd)
       return;
     }
 
-    if(!getaddressinfo((struct sockaddr*)&ssrem,
-                        conn->primary_ip, &conn->primary_port)) {
+    if(!Curl_getaddressinfo((struct sockaddr*)&ssrem,
+                            conn->primary_ip, &conn->primary_port)) {
       failf(data, "ssrem inet_ntop() failed with errno %d: %s",
             errno, Curl_strerror(conn, errno));
       return;
     }
     memcpy(conn->ip_addr_str, conn->primary_ip, MAX_IPADR_LEN);
 
-    if(!getaddressinfo((struct sockaddr*)&ssloc,
-                       conn->local_ip, &conn->local_port)) {
+    if(!Curl_getaddressinfo((struct sockaddr*)&ssloc,
+                            conn->local_ip, &conn->local_port)) {
       failf(data, "ssloc inet_ntop() failed with errno %d: %s",
             errno, Curl_strerror(conn, errno));
       return;
@@ -1005,8 +1005,8 @@ static CURLcode singleipconnect(struct connectdata *conn,
     return CURLE_OK;
 
   /* store remote address and port used in this connection attempt */
-  if(!getaddressinfo((struct sockaddr*)&addr.sa_addr,
-                     ipaddress, &port)) {
+  if(!Curl_getaddressinfo((struct sockaddr*)&addr.sa_addr,
+                          ipaddress, &port)) {
     /* malformed address or bug in inet_ntop, try next address */
     failf(data, "sa_addr inet_ntop() failed with errno %d: %s",
           errno, Curl_strerror(conn, errno));
diff --git a/lib/connect.h b/lib/connect.h
index 397448636..4c038874e 100644
--- a/lib/connect.h
+++ b/lib/connect.h
@@ -78,6 +78,11 @@ void Curl_persistconninfo(struct connectdata *conn);
 int Curl_closesocket(struct connectdata *conn, curl_socket_t sock);
 
 /*
+ * Get presentation format IP address and port from a sockaddr.
+ */
+bool Curl_getaddressinfo(struct sockaddr *sa, char *addr, long *port);
+
+/*
  * The Curl_sockaddr_ex structure is basically libcurl's external API
  * curl_sockaddr structure with enough space available to directly hold any
  * protocol-specific address structures. The variable declared here will be
diff --git a/lib/hostip.c b/lib/hostip.c
index 886aeec42..8310c83e1 100644
--- a/lib/hostip.c
+++ b/lib/hostip.c
@@ -781,7 +781,7 @@ CURLcode Curl_loadhostpairs(struct Curl_easy *data)
 {
   struct curl_slist *hostp;
   char hostname[256];
-  int port;
+  int port = 0;
 
   for(hostp = data->change.resolve; hostp; hostp = hostp->next) {
     if(!hostp->data)
@@ -819,32 +819,95 @@ CURLcode Curl_loadhostpairs(struct Curl_easy *data)
     }
     else {
       struct Curl_dns_entry *dns;
-      Curl_addrinfo *addr;
+      Curl_addrinfo *head = NULL, *tail = NULL;
       char *entry_id;
       size_t entry_len;
-      char buffer[256];
-      char *address = &buffer[0];
+      char address[64];
+      char *addresses;
+      char *addr_begin;
+      char *addr_end;
+      char *port_ptr;
+      char *end_ptr;
+      char *host_end;
+      unsigned long tmp_port;
+      bool error = true;
+
+      host_end = strchr(hostp->data, ':');
+      if(!host_end ||
+         ((host_end - hostp->data) >= (ptrdiff_t)sizeof(hostname)))
+        goto err;
+
+      memcpy(hostname, hostp->data, host_end - hostp->data);
+      hostname[host_end - hostp->data] = '\0';
+
+      port_ptr = host_end + 1;
+      tmp_port = strtoul(port_ptr, &end_ptr, 10);
+      if(end_ptr == port_ptr || tmp_port > USHRT_MAX || *end_ptr != ':')
+        goto err;
+
+      port = (int)tmp_port;
+      addresses = end_ptr + 1;
+
+      while(*end_ptr) {
+        size_t alen;
+        Curl_addrinfo *ai;
+
+        addr_begin = end_ptr + 1;
+        addr_end = strchr(addr_begin, ',');
+        if(!addr_end)
+          addr_end = addr_begin + strlen(addr_begin);
+        end_ptr = addr_end;
+
+        /* allow IP(v6) address within [brackets] */
+        if(*addr_begin == '[') {
+          if(addr_end == addr_begin || *(addr_end - 1) != ']')
+            goto err;
+          ++addr_begin;
+          --addr_end;
+        }
 
-      if(3 != sscanf(hostp->data, "%255[^:]:%d:%255s", hostname, &port,
-                     address)) {
-        infof(data, "Couldn't parse CURLOPT_RESOLVE entry '%s'!\n",
-              hostp->data);
-        continue;
-      }
+        alen = addr_end - addr_begin;
+        if(!alen)
+          continue;
 
-      /* allow IP(v6) address within [brackets] */
-      if(address[0] == '[') {
-        size_t alen = strlen(address);
-        if(address[alen-1] != ']')
-          /* it needs to also end with ] to be valid */
+        if(alen >= sizeof(address))
+          goto err;
+
+        memcpy(address, addr_begin, alen);
+        address[alen] = '\0';
+
+#ifndef ENABLE_IPV6
+        if(strchr(address, ':')) {
+          infof(data, "Ignoring resolve address '%s', missing IPv6 support.\n",
+                address);
           continue;
-        address[alen-1] = 0; /* zero terminate there */
-        address++; /* pass the open bracket */
+        }
+#endif
+
+        ai = Curl_str2addr(address, port);
+        if(!ai) {
+          infof(data, "Resolve address '%s' found illegal!\n", address);
+          goto err;
+        }
+
+        if(tail) {
+          tail->ai_next = ai;
+          tail = tail->ai_next;
+        }
+        else {
+          head = tail = ai;
+        }
       }
 
-      addr = Curl_str2addr(address, port);
-      if(!addr) {
-        infof(data, "Address in '%s' found illegal!\n", hostp->data);
+      if(!head)
+        goto err;
+
+      error = false;
+   err:
+      if(error) {
+        infof(data, "Couldn't parse CURLOPT_RESOLVE entry '%s'!\n",
+              hostp->data);
+        Curl_freeaddrinfo(head);
         continue;
       }
 
@@ -852,10 +915,9 @@ CURLcode Curl_loadhostpairs(struct Curl_easy *data)
       entry_id = create_hostcache_id(hostname, port);
       /* If we can't create the entry id, fail */
       if(!entry_id) {
-        Curl_freeaddrinfo(addr);
+        Curl_freeaddrinfo(head);
         return CURLE_OUT_OF_MEMORY;
       }
-
       entry_len = strlen(entry_id);
 
       if(data->share)
@@ -869,7 +931,7 @@ CURLcode Curl_loadhostpairs(struct Curl_easy *data)
 
       if(!dns) {
         /* if not in the cache already, put this host in the cache */
-        dns = Curl_cache_addr(data, addr, hostname, port);
+        dns = Curl_cache_addr(data, head, hostname, port);
         if(dns) {
           dns->timestamp = 0; /* mark as added by CURLOPT_RESOLVE */
           /* release the returned reference; the cache itself will keep the
@@ -880,19 +942,19 @@ CURLcode Curl_loadhostpairs(struct Curl_easy *data)
       else {
         /* this is a duplicate, free it again */
         infof(data, "RESOLVE %s:%d is already cached, %s not stored!\n",
-              hostname, port, address);
-        Curl_freeaddrinfo(addr);
+              hostname, port, addresses);
+        Curl_freeaddrinfo(head);
       }
 
       if(data->share)
         Curl_share_unlock(data, CURL_LOCK_DATA_DNS);
 
       if(!dns) {
-        Curl_freeaddrinfo(addr);
+        Curl_freeaddrinfo(head);
         return CURLE_OUT_OF_MEMORY;
       }
       infof(data, "Added %s:%d:%s to DNS cache\n",
-            hostname, port, address);
+            hostname, port, addresses);
     }
   }
   data->change.resolve = NULL; /* dealt with now */
diff --git a/tests/data/Makefile.inc b/tests/data/Makefile.inc
index 91e4dd924..892012988 100644
--- a/tests/data/Makefile.inc
+++ b/tests/data/Makefile.inc
@@ -172,7 +172,7 @@ test1525 test1526 test1527 test1528 test1529 test1530 test1531 test1532 \
 test1533 test1534 test1535 test1536 test1537 test1538 \
 test1540 \
 test1550 test1551 test1552 test1553 test1554 test1555 test1556 \
-test1600 test1601 test1602 test1603 test1604 test1605 test1606 \
+test1600 test1601 test1602 test1603 test1604 test1605 test1606 test1607 \
 \
 test1700 test1701 test1702 \
 \
diff --git a/tests/data/test1607 b/tests/data/test1607
new file mode 100644
index 000000000..9628324e4
--- /dev/null
+++ b/tests/data/test1607
@@ -0,0 +1,26 @@
+<testcase>
+<info>
+<keywords>
+unittest
+CURLOPT_RESOLVE
+</keywords>
+</info>
+
+#
+# Client-side
+<client>
+<server>
+none
+</server>
+<features>
+unittest
+</features>
+ <name>
+CURLOPT_RESOLVE parsing
+ </name>
+<tool>
+unit1607
+</tool>
+</client>
+
+</testcase>
diff --git a/tests/unit/Makefile.inc b/tests/unit/Makefile.inc
index bfb5c4d45..9a19f51d1 100644
--- a/tests/unit/Makefile.inc
+++ b/tests/unit/Makefile.inc
@@ -9,7 +9,7 @@ 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
+ unit1600 unit1601 unit1602 unit1603 unit1604 unit1605 unit1606 unit1607
 
 unit1300_SOURCES = unit1300.c $(UNITFILES)
 unit1300_CPPFLAGS = $(AM_CPPFLAGS)
@@ -85,3 +85,6 @@ unit1605_CPPFLAGS = $(AM_CPPFLAGS)
 
 unit1606_SOURCES = unit1606.c $(UNITFILES)
 unit1606_CPPFLAGS = $(AM_CPPFLAGS)
+
+unit1607_SOURCES = unit1607.c $(UNITFILES)
+unit1607_CPPFLAGS = $(AM_CPPFLAGS)
diff --git a/tests/unit/unit1607.c b/tests/unit/unit1607.c
new file mode 100644
index 000000000..3e53d4d20
--- /dev/null
+++ b/tests/unit/unit1607.c
@@ -0,0 +1,203 @@
+/***************************************************************************
+ *                                  _   _ ____  _
+ *  Project                     ___| | | |  _ \| |
+ *                             / __| | | | |_) | |
+ *                            | (__| |_| |  _ <| |___
+ *                             \___|\___/|_| \_\_____|
+ *
+ * Copyright (C) 1998 - 2018, Daniel Stenberg, <daniel@haxx.se>, 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 "urldata.h"
+#include "connect.h"
+#include "share.h"
+
+#include "memdebug.h" /* LAST include file */
+
+static struct Curl_easy *easy;
+struct curl_hash *hostcache;
+
+static CURLcode unit_setup(void)
+{
+  int res = CURLE_OK;
+
+  global_init(CURL_GLOBAL_ALL);
+
+  easy = curl_easy_init();
+  if(!easy)
+    return CURLE_OUT_OF_MEMORY;
+
+  hostcache = Curl_global_host_cache_init();
+  if(!hostcache)
+    return CURLE_OUT_OF_MEMORY;
+
+  return res;
+}
+
+static void unit_stop(void)
+{
+  curl_easy_cleanup(easy);
+  curl_global_cleanup();
+}
+
+struct testcase {
+  /* host:port:address[,address]... */
+  const char *optval;
+
+  /* lowercase host and port to retrieve the addresses from hostcache */
+  const char *host;
+  int port;
+
+  /* 0 to 9 addresses expected from hostcache */
+  const char *address[10];
+};
+
+
+/* In builds without IPv6 support CURLOPT_RESOLVE should skip over those
+   addresses, so we have to do that as well. */
+static const char skip = 0;
+#ifdef ENABLE_IPV6
+#define IPV6ONLY(x) x
+#else
+#define IPV6ONLY(x) &skip
+#endif
+
+/* CURLOPT_RESOLVE address parsing tests */
+static const struct testcase tests[] = {
+  /* spaces aren't allowed, for now */
+  { "test.com:80:127.0.0.1, 127.0.0.2",
+    "test.com", 80, { NULL, }
+  },
+  { "TEST.com:80:,,127.0.0.1,,,127.0.0.2,,,,::1,,,",
+    "test.com", 80, { "127.0.0.1", "127.0.0.2", IPV6ONLY("::1"), }
+  },
+  { "test.com:80:::1,127.0.0.1",
+    "test.com", 80, { IPV6ONLY("::1"), "127.0.0.1", }
+  },
+  { "test.com:80:[::1],127.0.0.1",
+    "test.com", 80, { IPV6ONLY("::1"), "127.0.0.1", }
+  },
+  { "test.com:80:::1",
+    "test.com", 80, { IPV6ONLY("::1"), }
+  },
+  { "test.com:80:[::1]",
+    "test.com", 80, { IPV6ONLY("::1"), }
+  },
+  { "test.com:80:127.0.0.1",
+    "test.com", 80, { "127.0.0.1", }
+  },
+  { "test.com:80:,127.0.0.1",
+    "test.com", 80, { "127.0.0.1", }
+  },
+  { "test.com:80:127.0.0.1,",
+    "test.com", 80, { "127.0.0.1", }
+  },
+  { "test.com:0:127.0.0.1",
+    "test.com", 0, { "127.0.0.1", }
+  },
+};
+
+UNITTEST_START
+  int i;
+  int testnum = sizeof(tests) / sizeof(struct testcase);
+
+  for(i = 0; i < testnum; ++i, curl_easy_reset(easy)) {
+    int j;
+    int addressnum = sizeof tests[i].address / sizeof *tests[i].address;
+    struct Curl_addrinfo *addr;
+    struct Curl_dns_entry *dns;
+    struct curl_slist *list;
+    void *entry_id;
+    bool problem = false;
+
+    Curl_hostcache_clean(easy, hostcache);
+    easy->dns.hostcache = hostcache;
+    easy->dns.hostcachetype = HCACHE_GLOBAL;
+
+    list = curl_slist_append(NULL, tests[i].optval);
+    curl_easy_setopt(easy, CURLOPT_RESOLVE, list);
+
+    Curl_loadhostpairs(easy);
+
+    entry_id = (void *)aprintf("%s:%d", tests[i].host, tests[i].port);
+    dns = Curl_hash_pick(easy->dns.hostcache, entry_id, strlen(entry_id) + 1);
+    free(entry_id);
+    entry_id = NULL;
+
+    addr = dns ? dns->addr : NULL;
+
+    for(j = 0; j < addressnum; ++j) {
+      long port = 0;
+      char ipaddress[MAX_IPADR_LEN] = {0};
+
+      if(!addr && !tests[i].address[j])
+        break;
+
+      if(tests[i].address[j] == &skip)
+        continue;
+
+      if(addr && !Curl_getaddressinfo(addr->ai_addr,
+                                      ipaddress, &port)) {
+        fprintf(stderr, "%s:%d tests[%d] failed. getaddressinfo failed.\n",
+                __FILE__, __LINE__, i);
+        problem = true;
+        break;
+      }
+
+      if(addr && !tests[i].address[j]) {
+        fprintf(stderr, "%s:%d tests[%d] failed. the retrieved addr "
+                "is %s but tests[%d].address[%d] is NULL.\n",
+                __FILE__, __LINE__, i, ipaddress, i, j);
+        problem = true;
+        break;
+      }
+
+      if(!addr && tests[i].address[j]) {
+        fprintf(stderr, "%s:%d tests[%d] failed. the retrieved addr "
+                "is NULL but tests[%d].address[%d] is %s.\n",
+                __FILE__, __LINE__, i, i, j, tests[i].address[j]);
+        problem = true;
+        break;
+      }
+
+      if(!curl_strequal(ipaddress, tests[i].address[j])) {
+        fprintf(stderr, "%s:%d tests[%d] failed. the retrieved addr "
+                "%s is not equal to tests[%d].address[%d] %s.\n",
+                __FILE__, __LINE__, i, ipaddress, i, j, tests[i].address[j]);
+        problem = true;
+        break;
+      }
+
+      if(port != tests[i].port) {
+        fprintf(stderr, "%s:%d tests[%d] failed. the retrieved port "
+                "for tests[%d].address[%d] is %ld but tests[%d].port is %d.\n",
+                __FILE__, __LINE__, i, i, j, port, i, tests[i].port);
+        problem = true;
+        break;
+      }
+
+      addr = addr->ai_next;
+    }
+
+    Curl_hostcache_clean(easy, easy->dns.hostcache);
+    curl_slist_free_all(list);
+
+    if(problem) {
+      unitfail++;
+      continue;
+    }
+  }
+UNITTEST_STOP