http_client: implement NO_PROXY support (#3272)

Signed-off-by: Yu Yi <[email protected]>

Author: erain

include/fluent-bit/flb_config.h

@@ -154,6 +154,16 @@ struct flb_config {
      */
     char *http_proxy;
 
+    /*
+     * A comma-separated list of host names that shouldn't go through
+     * any proxy is set in (only an asterisk, * matches all hosts).
+     * As a convention (https://curl.se/docs/manual.html), this value can be set
+     * and respected by `NO_PROXY` environment variable when `HTTP_PROXY` is used.
+     * Example: NO_PROXY="127.0.0.1,localhost,kubernetes.default.svc"
+     * Note: only `,` is allowed as seperator between URLs.
+     */
+    char *no_proxy;
+
     /* Chunk I/O Buffering */
     void *cio;
     char *storage_path;

include/fluent-bit/flb_str.h

@@ -58,4 +58,13 @@ static inline char *flb_strndup(const char *s, size_t n)
     return str;
 }
 
+/* emptyval checks whether a string has a non-null value "". */
+static inline int flb_str_emptyval(const char *s)
+{
+    if (s != NULL && strcmp(s, "") == 0) {
+        return FLB_TRUE;
+    }
+    return FLB_FALSE;
+}
+
 #endif

include/fluent-bit/flb_upstream.h

@@ -105,6 +105,6 @@ int flb_upstream_set_property(struct flb_config *config,
 int flb_upstream_is_async(struct flb_upstream *u);
 void flb_upstream_thread_safe(struct flb_upstream *u);
 struct mk_list *flb_upstream_get_config_map(struct flb_config *config);
-
+int flb_should_proxy_for_host(const char *host, const char *proxy, const char *no_proxy);
 
 #endif

src/flb_config.c

@@ -161,10 +161,15 @@ struct flb_config *flb_config_init()
 #endif
 
     config->http_proxy = getenv("HTTP_PROXY");
-    if (config->http_proxy != NULL && strcmp(config->http_proxy, "") == 0) {
+    if (flb_str_emptyval(config->http_proxy) == FLB_TRUE) {
         /* Proxy should not be set when the `HTTP_PROXY` is set to "" */
         config->http_proxy = NULL;
     }
+    config->no_proxy = getenv("NO_PROXY");
+    if (flb_str_emptyval(config->no_proxy) == FLB_TRUE || config->http_proxy == NULL) {
+        /* NoProxy  should not be set when the `NO_PROXYY` is set to "" or there is no Proxy. */
+        config->no_proxy = NULL;
+    }
 
     config->cio          = NULL;
     config->storage_path = NULL;

src/flb_upstream.c

@@ -185,7 +185,7 @@ struct flb_upstream *flb_upstream_create(struct flb_config *config,
     flb_net_setup_init(&u->net);
 
     /* Set upstream to the http_proxy if it is specified. */
-    if (config->http_proxy) {
+    if (flb_should_proxy_for_host(host, config->http_proxy, config->no_proxy) == FLB_TRUE) {
         flb_debug("[upstream] config->http_proxy: %s", config->http_proxy);
         ret = flb_utils_proxy_url_split(config->http_proxy, &proxy_protocol,
                                         &proxy_username, &proxy_password,
@@ -237,6 +237,39 @@ struct flb_upstream *flb_upstream_create(struct flb_config *config,
     return u;
 }
 
+/*
+ * Checks whehter a destinate URL should be proxied.
+ */
+int flb_should_proxy_for_host(const char *host, const char *proxy, const char *no_proxy)
+{
+    /* No HTTP_PROXY, should not set up proxy for the upstream `host`. */
+    if (proxy == NULL) {
+        return FLB_FALSE;
+    }
+
+    /* No NO_PROXY with HTTP_PROXY set, should set up proxy for the upstream `host`. */
+    if (no_proxy == NULL) {
+        return FLB_TRUE;
+    }
+
+    /* NO_PROXY=`*`, it matches all hosts. */
+    if (strcmp(no_proxy, "*") == 0) {
+        return FLB_FALSE;
+    }
+
+    /* check the URL list in the NO_PROXY  */
+    char *no_proxy_url = strtok(no_proxy, ",");
+    while (no_proxy_url != NULL) {
+        if (strcmp(host, no_proxy_url) == 0) {
+            return FLB_FALSE;
+        }
+        no_proxy_url = strtok(NULL, ",");
+    }
+
+    return FLB_TRUE;
+}
+
+
 
 /* Create an upstream context using a valid URL (protocol, host and port) */
 struct flb_upstream *flb_upstream_create_url(struct flb_config *config,