Minimize data sent in the default user agent (#14851)

src/porting.cpp

@@ -50,6 +50,7 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 #endif
 #if defined(__ANDROID__)
 	#include "porting_android.h"
+	#include <android/api-level.h>
 #endif
 #if defined(__APPLE__)
 	#include <mach-o/dyld.h>
@@ -205,7 +206,10 @@ bool detectMSVCBuildDir(const std::string &path)
 	return (!removeStringEnd(path, ends).empty());
 }
 
-std::string get_sysinfo()
+// Note that the system info is sent in every HTTP request, so keep it reasonably
+// privacy-conserving while ideally still being meaningful.
+
+static std::string detectSystemInfo()
 {
 #ifdef _WIN32
 	std::ostringstream oss;
@@ -251,14 +255,34 @@ std::string get_sysinfo()
 	delete[] filePath;
 
 	return oss.str();
-#else
+#elif defined(__ANDROID__)
+	std::ostringstream oss;
 	struct utsname osinfo;
 	uname(&osinfo);
-	return std::string(osinfo.sysname) + "/"
-		+ osinfo.release + " " + osinfo.machine;
+	int api = android_get_device_api_level();
+
+	oss << "Android/" << api << " " << osinfo.machine;
+	return oss.str();
+#else /* POSIX */
+	struct utsname osinfo;
+	uname(&osinfo);
+
+	std::string_view release(osinfo.release);
+	// cut off anything but the primary version number
+	release = release.substr(0, release.find_first_not_of("0123456789."));
+
+	std::string ret = osinfo.sysname;
+	ret.append("/").append(release).append(" ").append(osinfo.machine);
+	return ret;
 #endif
 }
 
+const std::string &get_sysinfo()
+{
+	static std::string ret = detectSystemInfo();
+	return ret;
+}
+
 
 bool getCurrentWorkingDir(char *buf, size_t len)
 {