Changeset f5a36ee in mod_gnutls

Timestamp:

Nov 11, 2015, 9:10:35 PM (3 years ago)

Author:

Thomas Klute <thomas2.klute@…>

Branches:

debian/master, debian/stretch-backports, jessie-backports, master, upstream

Children:

a63301f

Parents:

02a6a18

Message:

Pass EAGAIN/EINTR from gnutls_io_input_read to input filter

Unconditionally repeating calls to gnutls_record_recv on EAGAIN or
EINTR can lead to busy wait loops on nonblocking reads, which
particularly affects Keep-Alive connections waiting for new
requests. Passing the error code up to the filter instead lets the
higher levels deal with the interruption as appropriate in the given
context.

However, the input filter (mgs_filter_input) needs to handle a special
case for nonblocking reads: Those (strangely) return APR_EINTR if no
data is available. This has to be caught and APR_EAGAIN returned
instead, or mod_proxy will assume that the connection failed,
potentially breaking transmissions.

File:

• src/gnutls_io.c (modified) (2 diffs)

src/gnutls_io.c

@@ -241 +241 @@
     }
 
-    while (1) {
-
-        do
-            rc = gnutls_record_recv(ctxt->session, buf + bytes,
-                                    wanted - bytes);
-        while (rc == GNUTLS_E_INTERRUPTED || rc == GNUTLS_E_AGAIN);
+    while (1)
+    {
+        rc = gnutls_record_recv(ctxt->session, buf + bytes, wanted - bytes);
+
+        if (rc == GNUTLS_E_INTERRUPTED)
+            ctxt->input_rc = APR_EINTR;
+        else if (rc == GNUTLS_E_AGAIN)
+            ctxt->input_rc = APR_EAGAIN;
 
         if (rc > 0) {
@@ -557 +559 @@
     }
 
-    if (status != APR_SUCCESS) {
+    if (status != APR_SUCCESS)
+    {
+        /* no data for nonblocking read, return APR_EAGAIN */
+        if ((block == APR_NONBLOCK_READ) && (status == APR_EINTR))
+            return APR_EAGAIN;
+
         return gnutls_io_filter_error(f, bb, status);
     }