From 791e683e0150e0f3bc82416e6ecbf711bfd949c4 Mon Sep 17 00:00:00 2001
From: Juan RP <xtraeme@voidlinux.eu>
Date: Sun, 28 Jun 2015 04:28:55 +0200
Subject: [PATCH] fetch: handle GET with offset == length.

While xbps_fetch_file() creates the .part file and for whatever reason
it did not finish properly to rename the file, it could request the server
to restart the download with offset set to file size, resulting in HTTP 416
return code.

Handle this case by checking if the server returns 416 and then checking
if the returned file size matches the requested offset and just rename
the file.

Thanks to @beefcurtains for the test case.
---
 lib/download.c   |  5 +++++
 lib/fetch/http.c | 13 +++++++------
 2 files changed, 12 insertions(+), 6 deletions(-)

diff --git a/lib/download.c b/lib/download.c
index f2cd4a64..7dc67295 100644
--- a/lib/download.c
+++ b/lib/download.c
@@ -173,6 +173,9 @@ xbps_fetch_file_dest(struct xbps_handle *xhp, const char *uri, const char *filen
 		if (fetchLastErrCode == FETCH_UNCHANGED) {
 			/* Last-Modified matched */
 			goto fetch_file_out;
+		} else if (fetchLastErrCode == FETCH_PROTO && url_st.size == stp->st_size) {
+			/* 413, requested offset == length */
+			goto rename_file;
 		}
 		rv = -1;
 		goto fetch_file_out;
@@ -257,6 +260,7 @@ xbps_fetch_file_dest(struct xbps_handle *xhp, const char *uri, const char *filen
 	 */
 	xbps_set_cb_fetch(xhp, url_st.size, url->offset, bytes_dload,
 	    filename, false, false, true);
+
 	/*
 	 * Update mtime in local file to match remote file if transfer
 	 * was successful.
@@ -271,6 +275,7 @@ xbps_fetch_file_dest(struct xbps_handle *xhp, const char *uri, const char *filen
 	(void)close(fd);
 	fd = -1;
 
+rename_file:
 	/* File downloaded successfully, rename to destfile */
 	if (rename(tempfile, filename) == -1) {
 		xbps_dbg_printf(xhp, "failed to rename %s to %s: %s",
diff --git a/lib/fetch/http.c b/lib/fetch/http.c
index 25840a4c..f2d80bbe 100644
--- a/lib/fetch/http.c
+++ b/lib/fetch/http.c
@@ -1133,6 +1133,12 @@ http_request(struct url *URL, const char *op, struct url_stat *us,
 		goto ouch;
 	}
 
+	/* fill in stats */
+	if (us) {
+		us->size = size;
+		us->atime = us->mtime = mtime;
+	}
+
 	/* check for inconsistencies */
 	if (clength != -1 && length != -1 && clength != length) {
 		http_seterr(HTTP_PROTOCOL_ERROR);
@@ -1142,6 +1148,7 @@ http_request(struct url *URL, const char *op, struct url_stat *us,
 		clength = length;
 	if (clength != -1)
 		length = offset + clength;
+
 	if (length != -1 && size != -1 && length != size) {
 		http_seterr(HTTP_PROTOCOL_ERROR);
 		goto ouch;
@@ -1149,12 +1156,6 @@ http_request(struct url *URL, const char *op, struct url_stat *us,
 	if (size == -1)
 		size = length;
 
-	/* fill in stats */
-	if (us) {
-		us->size = size;
-		us->atime = us->mtime = mtime;
-	}
-
 	/* too far? */
 	if (URL->offset > 0 && offset > URL->offset) {
 		http_seterr(HTTP_PROTOCOL_ERROR);