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, 4 insertions, 0 deletions

diff --git a/plugins/check_curl.d/check_curl_helpers.h b/plugins/check_curl.d/check_curl_helpers.h
index 87e45a9d..e7b80f7e 100644
--- a/plugins/check_curl.d/check_curl_helpers.h
+++ b/plugins/check_curl.d/check_curl_helpers.h
@@ -7,6 +7,10 @@
 #       include <openssl/opensslv.h>
 #endif
 
+enum {
+        MAX_IPV4_HOSTLENGTH = 255,
+};
+
 /* for buffers for header and body */
 typedef struct {
         size_t buflen;