Account for the fact that sendfile(2) may hit the end of file

prematurely, e.g., if the file has been truncated by someone else.

PR:		bin/72649
Submitted by:	Oleg Koreshkov (portions)
MFC after:	2 weeks

1 files changed, 12 insertions, 1 deletions

diff --git a/libexec/ftpd/ftpd.c b/libexec/ftpd/ftpd.c
index 90373c6..f2aef51 100644
--- a/libexec/ftpd/ftpd.c
+++ b/libexec/ftpd/ftpd.c
@@ -2038,6 +2038,7 @@ send_data(FILE *instr, FILE *outstr, off_t blksize, off_t filesize, int isreg)
 
 		if (isreg) {
 
+			char *msg = "Transfer complete.";
 			off_t offset;
 			int err;
 
@@ -2062,10 +2063,20 @@ send_data(FILE *instr, FILE *outstr, off_t blksize, off_t filesize, int isreg)
 
 					goto data_err;
 				}
+
+				/*
+				 * We hit the EOF prematurely.
+				 * Perhaps the file was externally truncated.
+				 */
+				if (cnt == 0) {
+					msg = "Transfer finished due to "
+					      "premature end of file.";
+					break;
+				}
 			}
 
 			transflag = 0;
-			reply(226, "Transfer complete.");
+			reply(226, msg);
 			return (0);
 		}