svn commit: r225599 - head/usr.bin/fetch

[Dag-Erling Smorgrav]

Author: des
Date: Thu Sep 15 22:50:31 2011
New Revision: 225599
URL: http://svn.freebsd.org/changeset/base/225599

Log:
  When resuming an HTTP download, we failed to verify that the range
  returned by the server matched what we requested, and blindly appended
  what we received to what we already had.  This could go two ways: if the
  delivered offset was higher than expected, the local file would contain
  duplicate data, while if it was lower than expected, there would be data
  missing from the middle of the file.  Furthermore, if the transfer was
  interrupted again, each subsequent attempt would compound the error.
  Fix the first problem by restarting the transfer from scratch if there
  is a gap, and the second by explicitly seeking to the correct location
  in the local file so as to overwrite any duplicated data.
  
  PR:		bin/117277
  Approved by:	re (kib)
  MFC after:	3 weeks

Modified:
  head/usr.bin/fetch/fetch.c

Modified: head/usr.bin/fetch/fetch.c
==============================================================================
--- head/usr.bin/fetch/fetch.c	Thu Sep 15 22:14:35 2011	(r225598)
+++ head/usr.bin/fetch/fetch.c	Thu Sep 15 22:50:31 2011	(r225599)
@@ -522,6 +522,12 @@ fetch(char *URL, const char *path)
 				    "does not match remote", path);
 				goto failure_keep;
 			}
+		} else if (url->offset > sb.st_size) {
+			/* gap between what we asked for and what we got */
+			warnx("%s: gap in resume mode", URL);
+			fclose(of);
+			of = NULL;
+			/* picked up again later */
 		} else if (us.size != -1) {
 			if (us.size == sb.st_size)
 				/* nothing to do */
@@ -551,6 +557,14 @@ fetch(char *URL, const char *path)
 				fclose(of);
 				of = NULL;
 				sb = nsb;
+				/* picked up again later */
+			}
+			/* seek to where we left off */
+			if (of != NULL && fseek(of, url->offset, SEEK_SET) != 0) {
+				warn("%s: fseek()", path);
+				fclose(of);
+				of = NULL;
+				/* picked up again later */
 			}
 		}
 	} else if (m_flag && sb.st_size != -1) {