nghttpx: Android specific hack for special files for logging

Android lacks /dev/stderr, so directly use /proc/self/fd/2 as default
errorlog-file.  Android does not like O_APPEND for /proc/self/fd/1 and
/proc/self/fd/2, so omit the flag for these paths.

src/shrpx.cc

@@ -746,7 +746,12 @@ void fill_default_config()
   mod_config()->no_via = false;
   mod_config()->accesslog_file = nullptr;
   mod_config()->accesslog_syslog = false;
+#if defined(__ANDROID__) || defined(ANDROID)
+  // Android does not have /dev/stderr.  Use /proc/self/fd/2 instead.
+  mod_config()->errorlog_file = strcopy("/proc/self/fd/2");
+#else // !__ANDROID__ && ANDROID
   mod_config()->errorlog_file = strcopy("/dev/stderr");
+#endif // !__ANDROID__ && ANDROID
   mod_config()->errorlog_syslog = false;
   mod_config()->conf_path = strcopy("/etc/nghttpx/nghttpx.conf");
   mod_config()->syslog_facility = LOG_DAEMON;

src/util.cc

@@ -589,8 +589,24 @@ bool numeric_host(const char *hostname)
 
 int reopen_log_file(const char *path)
 {
+#if defined(__ANDROID__) || defined(ANDROID)
+  int fd;
+
+  if(strcmp("/proc/self/fd/1", path) == 0 ||
+     strcmp("/proc/self/fd/2", path) == 0) {
+
+    // We will get permission denied error when O_APPEND is used for
+    // these paths.
+    fd = open(path, O_WRONLY | O_CREAT | O_CLOEXEC,
+              S_IRUSR | S_IWUSR | S_IRGRP);
+  } else {
+    fd = open(path, O_WRONLY | O_APPEND | O_CREAT | O_CLOEXEC,
+              S_IRUSR | S_IWUSR | S_IRGRP);
+  }
+#else // !__ANDROID__ && !ANDROID
   auto fd = open(path, O_WRONLY | O_APPEND | O_CREAT | O_CLOEXEC,
                  S_IRUSR | S_IWUSR | S_IRGRP);
+#endif // !__ANDROID__ && !ANDROID
 
   if(fd == -1) {
     return -1;