Allow curl to rewind the read buffers

When using multi-pass authentication methods, the curl library may
need to rewind the read buffers (depending on how much already has
been fed to the server) used for providing data to HTTP PUT, POST or
PROPFIND, and in order to allow the library to do so, we need to tell
it how by providing either an ioctl callback or a seek callback.

This patch adds an ioctl callback, which should be usable on older
curl versions (since 7.12.3) than the seek callback (introduced in
curl 7.18.0).

Some HTTP servers (such as Apache) give an 401 error reply immediately
after receiving the headers (so no data has been read from the read
buffers, and thus no rewinding is needed), but other servers (such
as Lighttpd) only replies after the whole request has been sent and
all data has been read from the read buffers, making rewinding necessary.

Signed-off-by: Martin Storsjo <martin@martin.st>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

http-push.c

@@ -567,6 +567,10 @@ static void start_put(struct transfer_request *request)
 	curl_easy_setopt(slot->curl, CURLOPT_INFILE, &request->buffer);
 	curl_easy_setopt(slot->curl, CURLOPT_INFILESIZE, request->buffer.buf.len);
 	curl_easy_setopt(slot->curl, CURLOPT_READFUNCTION, fread_buffer);
+#ifndef NO_CURL_IOCTL
+	curl_easy_setopt(slot->curl, CURLOPT_IOCTLFUNCTION, ioctl_buffer);
+	curl_easy_setopt(slot->curl, CURLOPT_IOCTLDATA, &request->buffer);
+#endif
 	curl_easy_setopt(slot->curl, CURLOPT_WRITEFUNCTION, fwrite_null);
 	curl_easy_setopt(slot->curl, CURLOPT_CUSTOMREQUEST, DAV_PUT);
 	curl_easy_setopt(slot->curl, CURLOPT_UPLOAD, 1);
@@ -1267,6 +1271,10 @@ static struct remote_lock *lock_remote(const char *path, long timeout)
 	curl_easy_setopt(slot->curl, CURLOPT_INFILE, &out_buffer);
 	curl_easy_setopt(slot->curl, CURLOPT_INFILESIZE, out_buffer.buf.len);
 	curl_easy_setopt(slot->curl, CURLOPT_READFUNCTION, fread_buffer);
+#ifndef NO_CURL_IOCTL
+	curl_easy_setopt(slot->curl, CURLOPT_IOCTLFUNCTION, ioctl_buffer);
+	curl_easy_setopt(slot->curl, CURLOPT_IOCTLDATA, &out_buffer);
+#endif
 	curl_easy_setopt(slot->curl, CURLOPT_FILE, &in_buffer);
 	curl_easy_setopt(slot->curl, CURLOPT_WRITEFUNCTION, fwrite_buffer);
 	curl_easy_setopt(slot->curl, CURLOPT_URL, url);
@@ -1508,6 +1516,10 @@ static void remote_ls(const char *path, int flags,
 	curl_easy_setopt(slot->curl, CURLOPT_INFILE, &out_buffer);
 	curl_easy_setopt(slot->curl, CURLOPT_INFILESIZE, out_buffer.buf.len);
 	curl_easy_setopt(slot->curl, CURLOPT_READFUNCTION, fread_buffer);
+#ifndef NO_CURL_IOCTL
+	curl_easy_setopt(slot->curl, CURLOPT_IOCTLFUNCTION, ioctl_buffer);
+	curl_easy_setopt(slot->curl, CURLOPT_IOCTLDATA, &out_buffer);
+#endif
 	curl_easy_setopt(slot->curl, CURLOPT_FILE, &in_buffer);
 	curl_easy_setopt(slot->curl, CURLOPT_WRITEFUNCTION, fwrite_buffer);
 	curl_easy_setopt(slot->curl, CURLOPT_URL, url);
@@ -1584,6 +1596,10 @@ static int locking_available(void)
 	curl_easy_setopt(slot->curl, CURLOPT_INFILE, &out_buffer);
 	curl_easy_setopt(slot->curl, CURLOPT_INFILESIZE, out_buffer.buf.len);
 	curl_easy_setopt(slot->curl, CURLOPT_READFUNCTION, fread_buffer);
+#ifndef NO_CURL_IOCTL
+	curl_easy_setopt(slot->curl, CURLOPT_IOCTLFUNCTION, ioctl_buffer);
+	curl_easy_setopt(slot->curl, CURLOPT_IOCTLDATA, &out_buffer);
+#endif
 	curl_easy_setopt(slot->curl, CURLOPT_FILE, &in_buffer);
 	curl_easy_setopt(slot->curl, CURLOPT_WRITEFUNCTION, fwrite_buffer);
 	curl_easy_setopt(slot->curl, CURLOPT_URL, repo->url);
@@ -1766,6 +1782,10 @@ static int update_remote(unsigned char *sha1, struct remote_lock *lock)
 	curl_easy_setopt(slot->curl, CURLOPT_INFILE, &out_buffer);
 	curl_easy_setopt(slot->curl, CURLOPT_INFILESIZE, out_buffer.buf.len);
 	curl_easy_setopt(slot->curl, CURLOPT_READFUNCTION, fread_buffer);
+#ifndef NO_CURL_IOCTL
+	curl_easy_setopt(slot->curl, CURLOPT_IOCTLFUNCTION, ioctl_buffer);
+	curl_easy_setopt(slot->curl, CURLOPT_IOCTLDATA, &out_buffer);
+#endif
 	curl_easy_setopt(slot->curl, CURLOPT_WRITEFUNCTION, fwrite_null);
 	curl_easy_setopt(slot->curl, CURLOPT_CUSTOMREQUEST, DAV_PUT);
 	curl_easy_setopt(slot->curl, CURLOPT_HTTPHEADER, dav_headers);
@@ -1910,6 +1930,10 @@ static void update_remote_info_refs(struct remote_lock *lock)
 		curl_easy_setopt(slot->curl, CURLOPT_INFILE, &buffer);
 		curl_easy_setopt(slot->curl, CURLOPT_INFILESIZE, buffer.buf.len);
 		curl_easy_setopt(slot->curl, CURLOPT_READFUNCTION, fread_buffer);
+#ifndef NO_CURL_IOCTL
+		curl_easy_setopt(slot->curl, CURLOPT_IOCTLFUNCTION, ioctl_buffer);
+		curl_easy_setopt(slot->curl, CURLOPT_IOCTLDATA, &buffer);
+#endif
 		curl_easy_setopt(slot->curl, CURLOPT_WRITEFUNCTION, fwrite_null);
 		curl_easy_setopt(slot->curl, CURLOPT_CUSTOMREQUEST, DAV_PUT);
 		curl_easy_setopt(slot->curl, CURLOPT_HTTPHEADER, dav_headers);

http.c

@@ -44,6 +44,25 @@ size_t fread_buffer(void *ptr, size_t eltsize, size_t nmemb, void *buffer_)
 	return size;
 }
 
+#ifndef NO_CURL_IOCTL
+curlioerr ioctl_buffer(CURL *handle, int cmd, void *clientp)
+{
+	struct buffer *buffer = clientp;
+
+	switch (cmd) {
+	case CURLIOCMD_NOP:
+		return CURLIOE_OK;
+
+	case CURLIOCMD_RESTARTREAD:
+		buffer->posn = 0;
+		return CURLIOE_OK;
+
+	default:
+		return CURLIOE_UNKNOWNCMD;
+	}
+}
+#endif
+
 size_t fwrite_buffer(const void *ptr, size_t eltsize, size_t nmemb, void *buffer_)
 {
 	size_t size = eltsize * nmemb;

http.h

@@ -37,6 +37,10 @@
 #define CURLE_HTTP_RETURNED_ERROR CURLE_HTTP_NOT_FOUND
 #endif
 
+#if LIBCURL_VERSION_NUM < 0x070c03
+#define NO_CURL_IOCTL
+#endif
+
 struct slot_results
 {
 	CURLcode curl_result;
@@ -67,6 +71,9 @@ struct buffer
 extern size_t fread_buffer(void *ptr, size_t eltsize, size_t nmemb, void *strbuf);
 extern size_t fwrite_buffer(const void *ptr, size_t eltsize, size_t nmemb, void *strbuf);
 extern size_t fwrite_null(const void *ptr, size_t eltsize, size_t nmemb, void *strbuf);
+#ifndef NO_CURL_IOCTL
+extern curlioerr ioctl_buffer(CURL *handle, int cmd, void *clientp);
+#endif
 
 /* Slot lifecycle functions */
 extern struct active_request_slot *get_active_slot(void);