s3: smbd: Fix AIX sendfile() for SMB2. Ensure we don't spin on EAGAIN.

For SMB2 the socket is set non-blocking. Ensure sendfile()
calls complete if they return EAGAIN by saving the socket state,
setting it blocking, doing the sendfile until completion and then
restoring the socket state.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=13537

Signed-off-by: Jeremy Allison <jra@samba.org>
Reviewed-by: Volker Lendecke <vl@samba.org>
Autobuild-User(master): Volker Lendecke <vl@samba.org>
Autobuild-Date(master): Fri Jul 20 15:14:24 CEST 2018 on sn-devel-144

(cherry picked from commit 582ce5d6b599516d6d8d619529a2aa809139a175)

Autobuild-User(v4-7-test): Karolin Seeger <kseeger@samba.org>
Autobuild-Date(v4-7-test): Sat Jul 28 10:57:39 CEST 2018 on sn-devel-144

diff --git a/source3/lib/sendfile.c b/source3/lib/sendfile.c
index aa115948501e3a0603d010c928d40c0c0da08b42..d3effaf30aa4537d24741c59db3dbc4afefd9839 100644 (file)
--- a/source3/lib/sendfile.c
+++ b/source3/lib/sendfile.c
@@ -510,6 +510,9 @@ ssize_t sys_sendfile(int tofd, int fromfd,
 ssize_t sys_sendfile(int tofd, int fromfd, const DATA_BLOB *header, off_t offset, size_t count)
 {
        struct sf_parms hdtrl;
+       int old_flags = 0;
+       ssize_t ret = -1;
+       bool socket_flags_changed = false;
 
        /* Set up the header/trailer struct params. */
        if (header) {
@@ -527,8 +530,6 @@ ssize_t sys_sendfile(int tofd, int fromfd, const DATA_BLOB *header, off_t offset
        hdtrl.file_bytes = count;
 
        while ( hdtrl.file_bytes + hdtrl.header_length ) {
-               ssize_t ret;
-
                /*
                 Return Value
 
@@ -546,12 +547,50 @@ ssize_t sys_sendfile(int tofd, int fromfd, const DATA_BLOB *header, off_t offset
                */
                do {
                        ret = send_file(&tofd, &hdtrl, 0);
-               } while ((ret == 1) || (ret == -1 && (errno == EINTR || errno == EAGAIN || errno == EWOULDBLOCK)));
-               if ( ret == -1 )
+               } while ((ret == 1) || (ret == -1 && errno == EINTR));
+               if ( ret == -1 ) {
+                       if (errno == EAGAIN || errno == EWOULDBLOCK) {
+                               /*
+                                * Sendfile must complete before we can
+                                * send any other outgoing data on the socket.
+                                * Ensure socket is in blocking mode.
+                                * For SMB2 by default the socket is in
+                                * non-blocking mode.
+                                */
+                               old_flags = fcntl(tofd, F_GETFL, 0);
+                               ret = set_blocking(tofd, true);
+                               if (ret == -1) {
+                                       goto out;
+                               }
+                               socket_flags_changed = true;
+                               continue;
+                       }
+                       goto out;
+               }
+       }
+
+       ret = count + header->length;
+
+  out:
+
+       if (socket_flags_changed) {
+               int saved_errno;
+               int err;
+
+               if (ret == -1) {
+                       saved_errno = errno;
+               }
+               /* Restore the old state of the socket. */
+               err = fcntl(tofd, F_SETFL, old_flags);
+               if (err == -1) {
                        return -1;
+               }
+               if (ret == -1) {
+                       errno = saved_errno;
+               }
        }
 
-       return count + header->length;
+       return ret;
 }
 /* END AIX SEND_FILE */