s3: smbd: Fix FreeBSD 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>

diff --git a/source3/lib/sendfile.c b/source3/lib/sendfile.c
index 05e9a9b7cbd6e0216b041765c8e9b8d8b3e26084..aa115948501e3a0603d010c928d40c0c0da08b42 100644 (file)
--- a/source3/lib/sendfile.c
+++ b/source3/lib/sendfile.c
@@ -405,9 +405,11 @@ ssize_t sys_sendfile(int tofd, int fromfd,
 {
        struct sf_hdtr  sf_header = {0};
        struct iovec    io_header = {0};
+       int old_flags = 0;
 
        off_t   nwritten;
-       int     ret;
+       ssize_t ret = -1;
+       bool socket_flags_changed = false;
 
        if (header) {
                sf_header.headers = &io_header;
@@ -428,9 +430,26 @@ ssize_t sys_sendfile(int tofd, int fromfd,
 #else
                ret = sendfile(fromfd, tofd, offset, count, &sf_header, &nwritten, 0);
 #endif
-               if (ret == -1 && errno != EINTR && errno != EAGAIN && errno != EWOULDBLOCK) {
+               if (ret == -1 && errno != EINTR) {
+                       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;
+                       }
                        /* Send failed, we are toast. */
-                       return -1;
+                       ret = -1;
+                       goto out;
                }
 
                if (nwritten == 0) {
@@ -457,7 +476,28 @@ ssize_t sys_sendfile(int tofd, int fromfd,
                count -= nwritten;
        }
 
-       return nwritten;
+       ret = nwritten;
+
+  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 ret;
 }
 
 #elif defined(AIX_SENDFILE_API)