Fix/check curl sticky redir (#2188)

* check_curl: avoid freeing memory when we don't know where it came from

* check_curl: when using -f sticky conserve IPv6 addresses properly

When running the check on an ipv6 address with a sticky onredirect
policy like in this example:

  check_curl -6 -H example.com -I ::1 -f sticky

It results in a getaddrinfo error:

  HTTP CRITICAL - Unable to lookup IP address for '[::1]': getaddrinfo returned -3 - Temporary failure in name resolution

This happens because in check_http() if the content of server_addr is an
ipv6 address enclosing brackets are added and on redirection a
subsequent call to check_http() will pass this now bracketed value to
getaddrinfo resulting in the error.

To work around this, strip the brackets from the address prior to the
lookup_host() call.

* add Michael Jeanson to thanks

1 files changed, 13 insertions, 1 deletions

diff --git a/plugins/check_curl.d/check_curl_helpers.c b/plugins/check_curl.d/check_curl_helpers.c
index d49d8f07..e4e7bef6 100644
--- a/plugins/check_curl.d/check_curl_helpers.c
+++ b/plugins/check_curl.d/check_curl_helpers.c
@@ -128,8 +128,20 @@ check_curl_configure_curl(const check_curl_static_curl_config config,
         char dnscache[DEFAULT_BUFFER_SIZE];
         char addrstr[DEFAULT_BUFFER_SIZE / 2];
         if (working_state.use_ssl && working_state.host_name != NULL) {
+                char *tmp_mod_address;
+
+                /* lookup_host() requires an IPv6 address without the brackets. */
+                if ((strnlen(working_state.server_address, MAX_IPV4_HOSTLENGTH) > 2) &&
+                        (working_state.server_address[0] == '[')) {
+                        // Duplicate and strip the leading '['
+                        tmp_mod_address =
+                                strndup(working_state.server_address + 1, strlen(working_state.server_address) - 2);
+                } else {
+                        tmp_mod_address = working_state.server_address;
+                }
+
                 int res;
-                if ((res = lookup_host(working_state.server_address, addrstr, DEFAULT_BUFFER_SIZE / 2,
+                if ((res = lookup_host(tmp_mod_address, addrstr, DEFAULT_BUFFER_SIZE / 2,
                                                            config.sin_family)) != 0) {
                         die(STATE_CRITICAL,
                                 _("Unable to lookup IP address for '%s': getaddrinfo returned %d - %s"),