bb_info_msg: make it do atomic, unbuffered writes

udhcpc: fix a problem where we don't open listening socket fast enough

function                                             old     new   delta
bb_info_msg                                           70     126     +56
change_listen_mode                                    37      78     +41
udhcp_listen_socket                                  151     124     -27
udhcpc_main                                         2344    2285     -59

2 files changed, 42 insertions, 7 deletions

diff --git a/libbb/info_msg.c b/libbb/info_msg.c
index ffef05e54..8b8a1fcca 100644
--- a/libbb/info_msg.c
+++ b/libbb/info_msg.c
@@ -12,6 +12,7 @@
 
 void FAST_FUNC bb_info_msg(const char *s, ...)
 {
+#ifdef THIS_ONE_DOESNT_DO_SINGLE_WRITE
         va_list p;
         /* va_copy is used because it is not portable
          * to use va_list p twice */
@@ -27,4 +28,29 @@ void FAST_FUNC bb_info_msg(const char *s, ...)
                 vsyslog(LOG_INFO, s, p2);
         va_end(p2);
         va_end(p);
+#else
+        int used;
+        char *msg;
+        va_list p;
+
+        if (logmode == 0)
+                return;
+
+        va_start(p, s);
+        used = vasprintf(&msg, s, p);
+        if (used < 0)
+                return;
+
+        if (ENABLE_FEATURE_SYSLOG && (logmode & LOGMODE_SYSLOG))
+                syslog(LOG_INFO, "%s", msg);
+        if (logmode & LOGMODE_STDIO) {
+                fflush(stdout);
+                /* used = strlen(msg); - must be true already */
+                msg[used++] = '\n';
+                full_write(STDOUT_FILENO, msg, used);
+        }
+
+        free(msg);
+        va_end(p);
+#endif
 }
diff --git a/networking/udhcp/dhcpc.c b/networking/udhcp/dhcpc.c
index e2e5b0a82..115cddbf0 100644
--- a/networking/udhcp/dhcpc.c
+++ b/networking/udhcp/dhcpc.c
@@ -43,11 +43,17 @@ static void change_listen_mode(int new_mode)
 {
         DEBUG("entering %s listen mode",
                 new_mode ? (new_mode == 1 ? "kernel" : "raw") : "none");
+
+        listen_mode = new_mode;
         if (sockfd >= 0) {
                 close(sockfd);
                 sockfd = -1;
         }
-        listen_mode = new_mode;
+        if (new_mode == LISTEN_KERNEL)
+                sockfd = udhcp_listen_socket(/*INADDR_ANY,*/ CLIENT_PORT, client_config.interface);
+        else if (new_mode != LISTEN_NONE)
+                sockfd = udhcp_raw_socket(client_config.ifindex);
+        /* else LISTEN_NONE: sockfd stay closed */
 }
 
 
@@ -320,12 +326,15 @@ int udhcpc_main(int argc UNUSED_PARAM, char **argv)
         for (;;) {
                 unsigned timestamp_before_wait;
 
-                if (listen_mode != LISTEN_NONE && sockfd < 0) {
-                        if (listen_mode == LISTEN_KERNEL)
-                                sockfd = udhcp_listen_socket(/*INADDR_ANY,*/ CLIENT_PORT, client_config.interface);
-                        else
-                                sockfd = udhcp_raw_socket(client_config.ifindex);
-                }
+                //bb_error_msg("sockfd:%d, listen_mode:%d", sockfd, listen_mode);
+
+                /* Was opening raw or udp socket here
+                 * if (listen_mode != LISTEN_NONE && sockfd < 0),
+                 * but on fast network renew responses return faster
+                 * than we open sockets. Thus this code is moved
+                 * to change_listen_mode(). Thus we open listen socket
+                 * BEFORE we send renew request (see "case BOUND:"). */
+
                 max_fd = udhcp_sp_fd_set(&rfds, sockfd);
 
                 tv.tv_sec = timeout - already_waited_sec;