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document proxy cli arguments

Browse source 
clarify and add more examples of proxy environment variables and their
behavior when multiple are specified, overriden etc.

add single wildcard '*' checking for no_proxy to
determine_hostname_resolver, special case per curlopt_noproxy
documentation
This commit is contained in:
Ahmet Oeztuerk 2026-01-07 16:30:33 +01:00
parent cfeaf28338
commit 5e618a31a0
2 changed files with 57 additions and 15 deletions
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58
plugins/check_curl.c
View file

@ -1533,8 +1533,8 @@ void print_help(void) {
printf(" %s\n", "-I, --IP-address=ADDRESS");
printf(" %s\n",
"IP address or name (use numeric address if possible to bypass DNS lookup).");
printf(" %s\n", "This overwrites the network address of the target while leaving everything "
"else (HTTP headers) as they are");
printf(" %s\n",
"This overwrites the network address of the target while leaving everything else (HTTP headers) as they are");
printf(" %s\n", "-p, --port=INTEGER");
printf(" %s", _("Port number (default: "));
printf("%d)\n", HTTP_PORT);
@ -1598,8 +1598,7 @@ void print_help(void) {
printf(" %s\n", _("String to expect in the content"));
printf(" %s\n", "-u, --url=PATH");
printf(" %s\n", _("URL to GET or POST (default: /)"));
printf(" %s\n", _("This is the part after the address in a URL, so for "
"\"https://example.com/index.html\" it would be '-u /index.html'"));
printf(" %s\n", _("This is the part after the address in a URL, so for \"https://example.com/index.html\" it would be '-u /index.html'"));
printf(" %s\n", "-P, --post=STRING");
printf(" %s\n", _("URL decoded http POST data"));
printf(" %s\n",
@ -1630,6 +1629,13 @@ void print_help(void) {
printf(" %s\n", _("Available schemes are http, https, socks4, socks4a, socks5, socks5h"));
printf(" %s\n", _("If port is not specified, libcurl defaults to 1080"));
printf(" %s\n", _("This value will be set as CURLOPT_PROXY"));
printf(" %s\n", "--no-proxy=COMMA_SEPARATED_LIST");
printf(" %s\n", _("Specify hostnames, addresses and subnets where proxy should not be used"));
printf(" %s\n", _("Example usage: \"example.com,::1,1.1.1.1,localhost,192.168.0.0/16\""));
printf(" %s\n", _("Do not use brackets when specifying IPv6 addresses"));
printf(" %s\n", _("Special case when an item is '*' : matches all hosts/addresses "
"and effectively disables proxy."));
printf(" %s\n", _("This value will be set as CURLOPT_NOPROXY"));
printf(" %s\n", "-a, --authorization=AUTH_PAIR");
printf(" %s\n", _("Username:password on sites with basic authentication"));
printf(" %s\n", "-b, --proxy-authorization=AUTH_PAIR");
@ -1738,18 +1744,39 @@ void print_help(void) {
#endif
printf("\n %s\n", "CHECK WEBSERVER CONTENT VIA PROXY:");
printf(" %s\n", _("Proxies are defined checked using the -x or --proxy parameter:"));
printf(" %s\n",
_("The environment variables are only checked -x/--proxy arguments are not set:"));
printf(" %s\n", _("Depending on the SSL enablement, either http_proxy or https_proxy "
"environment variable is used."));
printf(" %s\n", _("These variables can also be given in uppercase, but the lowercase ones will "
printf(" %s\n", _("Proxies are specified or disabled for certain hosts/addresses using environment variables"
" or -x/--proxy and --no-proxy arguments:"));
printf(" %s\n", _("Checked environment variables: all_proxy, http_proxy, https_proxy, no_proxy"));
printf(" %s\n", _("Environment variables can also be given in uppercase, but the lowercase ones will "
"take predence if both are defined."));
printf(" %s\n",
_("http_proxy=http://192.168.100.35:3128 ./check_curl -H www.monitoring-plugins.org"));
printf(" %s\n", _("HTTPS_PROXY=http://192.168.100.35:3128 ./check_curl -H "
"www.monitoring-plugins.org --ssl"));
printf(" %s\n", _("legacy proxy requests in check_http style still work:"));
printf(" %s\n", _("The environment variables are overwritten by -x/--proxy and --no-proxy arguments:"));
printf(" %s\n", _("all_proxy/ALL_PROXY environment variables are read first, but protocol "
"specific environment variables override them."));
printf(" %s\n", _("If SSL is enabled and used, https_proxy/HTTPS_PROXY will be checked and overwrite "
"http_proxy/HTTPS_PROXY."));
printf(" %s\n", _("Curl accepts proxies using http, https, socks4, socks4a, socks5 and socks5h schemes."));
printf(" %s\n", _("http_proxy=http://192.168.100.35:3128 ./check_curl -H www.monitoring-plugins.org"));
printf(" %s\n", _("http_proxy=http://used.proxy.com HTTP_PROXY=http://ignored.proxy.com ./check_curl -H www.monitoring-plugins.org"));
printf(" %s\n", _(" Lowercase http_proxy takes predence over uppercase HTTP_PROXY"));
printf(" %s\n", _("./check_curl -H www.monitoring-plugins.org -x http://192.168.100.35:3128"));
printf(" %s\n", _("http_proxy=http://unused.proxy1.com HTTP_PROXY=http://unused.proxy2.com ./check_curl "
"-H www.monitoring-plugins.org --proxy http://used.proxy"));
printf(" %s\n", _(" Proxy specified by --proxy overrides any proxy specified by environment variable."));
printf(" %s\n", _(" Curl uses port 1080 by default as port is not specified"));
printf(" %s\n", _("HTTPS_PROXY=http://192.168.100.35:3128 ./check_curl -H www.monitoring-plugins.org --ssl"));
printf(" %s\n", _(" HTTPS_PROXY is read as --ssl is toggled"));
printf(" %s\n", _("./check_curl -H www.monitoring-plugins.org --proxy socks5h://192.168.122.21"));
printf(" %s\n", _("./check_curl -H www.monitoring-plugins.org -x http://unused.proxy.com --no-proxy '*'"));
printf(" %s\n", _(" Disabled proxy for all hosts by using '*' in no_proxy ."));
printf(" %s\n", _("NO_PROXY=www.monitoring-plugins.org ./check_curl -H www.monitoring-plugins.org -x http://unused.proxy.com"));
printf(" %s\n", _(" Exact matches with the hostname/address work."));
printf(" %s\n", _("no_proxy=192.168.178.0/24 ./check_curl -I 192.168.178.10 -x http://proxy.acme.org"));
printf(" %s\n", _("no_proxy=acme.org ./check_curl -H nonpublic.internalwebapp.acme.org -x http://proxy.acme.org"));
printf(" %s\n", _(" Do not use proxy when accessing internal domains/addresses, but use a default proxy when accessing public web."));
printf(" %s\n", _(" IMPORTANT: Check_curl can not always determine whether itself or the proxy will "
"resolve a hostname before sending a request and getting an answer."
"This can lead to DNS resolvation issues if hostname is only resolvable over proxy."));
printf(" %s\n", _("Legacy proxy requests in check_http style still work:"));
printf(" %s\n", _("check_curl -I 192.168.100.35 -p 3128 -u http://www.monitoring-plugins.org/ "
"-H www.monitoring-plugins.org"));
@ -1788,6 +1815,7 @@ void print_usage(void) {
printf(" [-P string] [-m <min_pg_size>:<max_pg_size>] [-4|-6] [-N] [-M <age>]\n");
printf(" [-A string] [-k string] [-S <version>] [--sni] [--haproxy-protocol]\n");
printf(" [-T <content-type>] [-j method]\n");
printf(" [--no-proxy=<comma separated list of hosts, IP addresses, IP CIDR subnets>\n");
printf(" [--http-version=<version>] [--enable-automatic-decompression]\n");
printf(" [--cookie-jar=<cookie jar file>\n");
printf(" %s -H <vhost> | -I <IP-address> -C <warn_age>[,<crit_age>]\n", progname);

14
plugins/check_curl.d/check_curl_helpers.c
View file

@ -1421,6 +1421,18 @@ int determine_hostname_resolver(const check_curl_working_state working_state, co
char* noproxy_item = strtok(curlopt_noproxy_copy, ",");
while(noproxy_item != NULL){
/* CURLOPT_NOPROXY documentation: */
/* The only wildcard available is a single * character, which matches all hosts, and effectively disables the proxy. */
if ( strlen(noproxy_item) == 1 && noproxy_item[0] == '*'){
if (verbose >= 1){
printf("* noproxy includes '*' which disables proxy for all hosts including: %s or server_addresses including: %s\n", host_name_display , server_address_clean);
}
free(curlopt_noproxy_copy);
free(server_address_clean);
return 0;
}
/* direct comparison with the server_address */
if( server_address_clean != NULL && strlen(server_address_clean) == strlen(noproxy_item) && strcmp(server_address_clean, noproxy_item) == 0){
if (verbose >= 1){
@ -1441,6 +1453,8 @@ int determine_hostname_resolver(const check_curl_working_state working_state, co
return 0;
}
/* TODO: determine if the hostname is a subdomain of the item, e.g www.example.com when token is example.com*/
/* TODO: determine if its IPv4 or IPv6 CIDR notation, if a server_address is used check if its in the subnet specified by CIDR */
if (verbose >= 1){