nix: Fix haveInternet to check for proxy

src/nix/main.cc

@@ -23,6 +23,7 @@
 #include <netdb.h>
 #include <netinet/in.h>
 #include <regex>
+#include <cstdlib>
 
 #include <nlohmann/json.hpp>
 
@@ -32,6 +33,24 @@ void chrootHelper(int argc, char * * argv);
 
 namespace nix {
 
+static bool haveProxyEnvironmentVariables()
+{
+    static const char * const proxyVariables[] = {
+        "http_proxy",
+        "https_proxy",
+        "ftp_proxy",
+        "HTTP_PROXY",
+        "HTTPS_PROXY",
+        "FTP_PROXY"
+    };
+    for (auto & proxyVariable: proxyVariables) {
+        if (std::getenv(proxyVariable)) {
+            return true;
+        }
+    }
+    return false;
+}
+
 /* Check if we have a non-loopback/link-local network interface. */
 static bool haveInternet()
 {
@@ -55,6 +74,8 @@ static bool haveInternet()
         }
     }
 
+    if (haveProxyEnvironmentVariables()) return true;
+
     return false;
 }