Re: [Bug 3610] New: kernel-2.6.9 breaks Amanda

[Stephen Hemminger <shemminger@xxxxxxxx>]

Try the following patch to amanda that resolves potential
issues with UDP and blocking receive.

--- amanda-2.4.4p3/common-src/dgram.c.orig      2004-10-26 09:51:27.000000000 
-0700
+++ amanda-2.4.4p3/common-src/dgram.c   2004-10-26 10:01:56.622775784 -0700
@@ -248,9 +248,31 @@
     socklen_t addrlen;
     int nfound;
     int save_errno;
+    int flags;
 
     sock = dgram->socket;
 
+    /* Need to be in non-blocking mode before doing receive,
+     * because select on Linux will return true when there is
+     * a UDP message with checksum error, but receive will
+     * then hang.
+     */
+    flags = fcntl(sock, F_GETFL);
+    if (flags < 0) {
+           save_errno = errno;
+           dbprintf(("%s: dgram_recv: fcntl get flags failed %s\n",
+                     debug_prefix(NULL), strerror(save_errno)));
+           return -1;
+    }               
+
+    if(fcntl(sock, F_SETFL, flags|O_NONBLOCK) < 0) {
+           save_errno = errno;
+           dbprintf(("%s: dgram_recv: fcntl set flags failed %s\n",
+                     debug_prefix(NULL), strerror(save_errno)));
+           return -1;
+    }               
+
+ retry:
     FD_ZERO(&ready);
     FD_SET(sock, &ready);
     to.tv_sec = timeout;
@@ -284,6 +306,7 @@
            nfound = -1;
        }
        errno = save_errno;
+       fcntl(sock, F_SETFL, flags);
        return nfound;
     }
 
@@ -291,13 +314,19 @@
     size = recvfrom(sock, dgram->data, MAX_DGRAM, 0,
                    (struct sockaddr *)fromaddr, &addrlen);
     if(size == -1) {
+       if (errno == EINTR || errno == EAGAIN)
+               goto retry;
        save_errno = errno;
        dbprintf(("%s: dgram_recv: recvfrom() failed: %s\n",
                  debug_prefix(NULL),
                  strerror(save_errno)));
        errno = save_errno;
+       fcntl(sock, F_SETFL, flags);
        return -1;
     }
+
+    fcntl(sock, F_SETFL, flags);
+
     dgram->len = size;
     dgram->data[size] = '\0';
     dgram->cur = dgram->data;