pop3-pluging blocks on read

[whaslbeck@…]

I discovered that lcd4linux stops updating the display after some time (about 2 or 3 days). I've done some resarch and discoverd that lcd4linux hangs inside the pop3-plugin. After attaching gdb to the running process, I get the following stacktrace:

(gdb) bt
#0  0xb7d832ce in read () from /lib/tls/libc.so.6
#1  0x08058ac3 in pop3_recv_crlf_terminated (sockfd=8, buf=0xbfc6a9c0 "", size=8192) at plugin_pop3.c:234
#2  0x08058d44 in my_POP3check (result=0x806d8d0, check=0x806d908) at plugin_pop3.c:188
#3  0x0804d72d in EvalTree (Root=0x806d8b0) at evaluator.c:1085
#4  0x0804ddd7 in Eval (tree=0x806d8b0, result=0xbfc6cb34) at evaluator.c:1294
#5  0x08050230 in widget_text_update (Self=0x8077230) at widget_text.c:280
#6  0x0804f066 in timer_process (delay=0xbfc6cbf0) at timer.c:196
#7  0x0804adbb in main (argc=4, argv=0xbfc6cc94) at lcd4linux.c:684

when I set the stackframe up to my_POP3check() and return to the application, the applicaton continues running.

So I think the read() inside pop3_recv_crlf_terminated() should be nonblocking/timeout'ed (with select() or poll()).

Regards, Walter

[whaslbeck@…]

I added a timeout to the read() some hours ago. It runs - until now, here is the patch against current public-CVS-version:

--- plugin_pop3.c.orig	2005-12-30 17:40:26.000000000 +0100
+++ plugin_pop3.c	2005-12-30 17:40:44.000000000 +0100
@@ -81,6 +81,8 @@
 #include <unistd.h>
 /*#include <pwd.h> */
 #include <stdio.h>
+#include <sys/poll.h>
+#include <errno.h>
 
 #ifdef WITH_DMALLOC
 #include <dmalloc.h>
@@ -227,11 +229,28 @@
 static void pop3_recv_crlf_terminated(int sockfd, char *buf, int size)
 {
     /* receive one line server responses terminated with CRLF */
-    char *pos;
+    char *pos = buf;
     int bytes = 0;
+    struct pollfd rfd;
+    rfd.fd = sockfd;
+    rfd.events = POLLIN | POLLPRI;
     memset(buf, 0, size);
-    while ((pos = strstr(buf, "\r\n")) == NULL)
-	bytes += read(sockfd, buf + bytes, size - bytes);
+
+    while ((pos = strstr(buf, "\r\n")) == NULL) {
+	switch (poll(&rfd, 1, 1000) ) {
+	    case -1:
+		/* error */
+		error("[POP3] poll error: %d (%s)\n", errno, strerror(errno));
+		return;
+	    case 0:
+		/* timeout */
+		error("[POP3] poll timeout\n");
+		break;
+	    default:
+		bytes += read(sockfd, buf + bytes, size - bytes);
+	}
+    }
+
     *pos = '\0';
 }