r3944: Fix the problem we get on Linux where sendfile fails, but we've already sent the

header using send(). As our implementation of sendfile can't return EINTR (it
restarts in that case) use an errno of EINTR to signal the linux sendfile fail
after header case. When that happens send the rest of the data and then turn
off sendfile. Sendfile should be safe to enable on all systems now (even though
it may not help in all performance cases).
Jeremy.
(This used to be commit 78236382f7ffe08d7924907be49493779521837f)

2 files changed, 93 insertions, 17 deletions

diff --git a/source3/lib/sendfile.c b/source3/lib/sendfile.c
index 4aa76a0c74..75fb635fa2 100644
--- a/source3/lib/sendfile.c
+++ b/source3/lib/sendfile.c
@@ -65,8 +65,20 @@ ssize_t sys_sendfile(int tofd, int fromfd, const DATA_BLOB *header, SMB_OFF_T of
 			nwritten = sendfile(tofd, fromfd, &offset, total);
 #endif
 		} while (nwritten == -1 && errno == EINTR);
-		if (nwritten == -1)
+		if (nwritten == -1) {
+			if (errno == ENOSYS) {
+				/* Ok - we're in a world of pain here. We just sent
+				 * the header, but the sendfile failed. We have to
+				 * emulate the sendfile at an upper layer before we
+				 * disable it's use. So we do something really ugly.
+				 * We set the errno to a strange value so we can detect
+				 * this at the upper level and take care of it without
+				 * layer violation. JRA.
+				 */
+				errno = EINTR; /* Normally we can never return this. */
+			}
 			return -1;
+		}
 		if (nwritten == 0)
 			return -1; /* I think we're at EOF here... */
 		total -= nwritten;
@@ -131,8 +143,20 @@ ssize_t sys_sendfile(int tofd, int fromfd, const DATA_BLOB *header, SMB_OFF_T of
 		do {
 			nwritten = sendfile(tofd, fromfd, &small_offset, small_total);
 		} while (nwritten == -1 && errno == EINTR);
-		if (nwritten == -1)
+		if (nwritten == -1) {
+			if (errno == ENOSYS) {
+				/* Ok - we're in a world of pain here. We just sent
+				 * the header, but the sendfile failed. We have to
+				 * emulate the sendfile at an upper layer before we
+				 * disable it's use. So we do something really ugly.
+				 * We set the errno to a strange value so we can detect
+				 * this at the upper level and take care of it without
+				 * layer violation. JRA.
+				 */
+				errno = EINTR; /* Normally we can never return this. */
+			}
 			return -1;
+		}
 		if (nwritten == 0)
 			return -1; /* I think we're at EOF here... */
 		small_total -= nwritten;
diff --git a/source3/smbd/reply.c b/source3/smbd/reply.c
index a3bb412578..f8f6a14067 100644
--- a/source3/smbd/reply.c
+++ b/source3/smbd/reply.c
@@ -1717,7 +1717,7 @@ int reply_unlink(connection_struct *conn, char *inbuf,char *outbuf, int dum_size
  Fail for readbraw.
 ****************************************************************************/
 
-void fail_readraw(void)
+static void fail_readraw(void)
 {
 	pstring errstr;
 	slprintf(errstr, sizeof(errstr)-1, "FAIL ! reply_readbraw: socket write fail (%s)",
@@ -1725,12 +1725,46 @@ void fail_readraw(void)
 	exit_server(errstr);
 }
 
+#if defined(WITH_SENDFILE)
+/****************************************************************************
+ Fake (read/write) sendfile. Returns -1 on read or write fail.
+****************************************************************************/
+
+static ssize_t fake_sendfile(files_struct *fsp, SMB_OFF_T startpos, size_t nread, char *buf, int bufsize)
+{
+	ssize_t ret=0;
+
+	/* Paranioa check... */
+	if (nread > bufsize) {
+		fail_readraw();
+	}
+
+	if (nread > 0) {
+		ret = read_file(fsp,buf,startpos,nread);
+		if (ret == -1) {
+			return -1;
+		}
+	}
+
+	/* If we had a short read, fill with zeros. */
+	if (ret < nread) {
+		memset(buf, '\0', nread - ret);
+	}
+
+	if (write_data(smbd_server_fd(),buf,nread) != nread) {
+		return -1;
+	}	
+
+	return (ssize_t)nread;
+}
+#endif
+
 /****************************************************************************
  Use sendfile in readbraw.
 ****************************************************************************/
 
 void send_file_readbraw(connection_struct *conn, files_struct *fsp, SMB_OFF_T startpos, size_t nread,
-		ssize_t mincount, char *outbuf)
+		ssize_t mincount, char *outbuf, int out_buffsize)
 {
 	ssize_t ret=0;
 
@@ -1752,12 +1786,21 @@ void send_file_readbraw(connection_struct *conn, files_struct *fsp, SMB_OFF_T st
 
 		if ( SMB_VFS_SENDFILE( smbd_server_fd(), fsp, fsp->fd, &header, startpos, nread) == -1) {
 			/*
-			 * Special hack for broken Linux with no 64 bit clean sendfile. If we
-			 * return ENOSYS then pretend we just got a normal read.
+			 * Special hack for broken Linux with no working sendfile. If we
+			 * return EINTR we sent the header but not the rest of the data.
+			 * Fake this up by doing read/write calls.
 			 */
-			if (errno == ENOSYS) {
+			if (errno == EINTR) {
+				/* Ensure we don't do this again. */
 				set_use_sendfile(SNUM(conn), False);
-				goto normal_read;
+				DEBUG(0,("send_file_readbraw: sendfile not available. Faking..\n"));
+
+				if (fake_sendfile(fsp, startpos, nread, outbuf + 4, out_buffsize - 4) == -1) {
+					DEBUG(0,("send_file_readbraw: fake_sendfile failed for file %s (%s).\n",
+						fsp->fsp_name, strerror(errno) ));
+					exit_server("send_file_readbraw fake_sendfile failed");
+				}
+				return;
 			}
 
 			DEBUG(0,("send_file_readbraw: sendfile failed for file %s (%s). Terminating\n",
@@ -1767,7 +1810,6 @@ void send_file_readbraw(connection_struct *conn, files_struct *fsp, SMB_OFF_T st
 
 	}
 
-  normal_read:
 #endif
 
 	if (nread > 0) {
@@ -1790,7 +1832,7 @@ void send_file_readbraw(connection_struct *conn, files_struct *fsp, SMB_OFF_T st
  Reply to a readbraw (core+ protocol).
 ****************************************************************************/
 
-int reply_readbraw(connection_struct *conn, char *inbuf, char *outbuf, int dum_size, int dum_buffsize)
+int reply_readbraw(connection_struct *conn, char *inbuf, char *outbuf, int dum_size, int out_buffsize)
 {
 	extern struct current_user current_user;
 	ssize_t maxcount,mincount;
@@ -1905,7 +1947,7 @@ int reply_readbraw(connection_struct *conn, char *inbuf, char *outbuf, int dum_s
 	DEBUG( 3, ( "readbraw fnum=%d start=%.0f max=%d min=%d nread=%d\n", fsp->fnum, (double)startpos,
 				(int)maxcount, (int)mincount, (int)nread ) );
   
-	send_file_readbraw(conn, fsp, startpos, nread, mincount, outbuf);
+	send_file_readbraw(conn, fsp, startpos, nread, mincount, outbuf, out_buffsize);
 
 	DEBUG(5,("readbraw finished\n"));
 	END_PROFILE(SMBreadbraw);
@@ -2069,7 +2111,7 @@ Returning short read of maximum allowed for compatibility with Windows 2000.\n",
  Reply to a read and X - possibly using sendfile.
 ****************************************************************************/
 
-int send_file_readX(connection_struct *conn, char *inbuf,char *outbuf,int length, 
+int send_file_readX(connection_struct *conn, char *inbuf,char *outbuf,int length, int len_outbuf,
 		files_struct *fsp, SMB_OFF_T startpos, size_t smb_maxcnt)
 {
 	ssize_t nread = -1;
@@ -2117,12 +2159,22 @@ int send_file_readX(connection_struct *conn, char *inbuf,char *outbuf,int length
 
 		if ( SMB_VFS_SENDFILE( smbd_server_fd(), fsp, fsp->fd, &header, startpos, smb_maxcnt) == -1) {
 			/*
-			 * Special hack for broken Linux with no 64 bit clean sendfile. If we
-			 * return ENOSYS then pretend we just got a normal read.
+			 * Special hack for broken Linux with no working sendfile. If we
+			 * return EINTR we sent the header but not the rest of the data.
+			 * Fake this up by doing read/write calls.
 			 */
-			if (errno == ENOSYS) {
+			if (errno == EINTR) {
+				/* Ensure we don't do this again. */
 				set_use_sendfile(SNUM(conn), False);
-				goto normal_read;
+				DEBUG(0,("send_file_readX: sendfile not available. Faking..\n"));
+
+				if ((nread = fake_sendfile(fsp, startpos, smb_maxcnt, data,
+							len_outbuf - (data-outbuf))) == -1) {
+					DEBUG(0,("send_file_readX: fake_sendfile failed for file %s (%s).\n",
+						fsp->fsp_name, strerror(errno) ));
+					exit_server("send_file_readX: fake_sendfile failed");
+				}
+				return nread;
 			}
 
 			DEBUG(0,("send_file_readX: sendfile failed for file %s (%s). Terminating\n",
@@ -2223,7 +2275,7 @@ int reply_read_and_X(connection_struct *conn, char *inbuf,char *outbuf,int lengt
 		return ERROR_DOS(ERRDOS,ERRlock);
 	}
 
-	nread = send_file_readX(conn, inbuf, outbuf, length, fsp, startpos, smb_maxcnt);
+	nread = send_file_readX(conn, inbuf, outbuf, length, bufsize, fsp, startpos, smb_maxcnt);
 	if (nread != -1)
 		nread = chain_reply(inbuf,outbuf,length,bufsize);