[*] Support hop-counting in request header, protocol version 3

We steal 8 bits from the request offset to count hops when requests
get relayed by proxies. This still leaves plenty of bits for the
offset (56 bits, supporting images of up to 72 petabytes).
This is used to detect proxy cycles. The algorithm is not perfect
but should prevent endless relays of the same request.
This is backwards compatible to old clients and servers, as the server
only ever sets the hopcount in relayed requests if the upstream server
is using protocol version 3 or newer, and clients are automatically
upwards compatible as there is practically no image larger than 74PB,
so the newly introduced hop count field is always 0 even in requests
from old clients.

1 files changed, 2 insertions, 2 deletions

diff --git a/src/server/uplink.h b/src/server/uplink.h
index c8cf4eb..2b41dfc 100644
--- a/src/server/uplink.h
+++ b/src/server/uplink.h
@@ -8,11 +8,11 @@ void uplink_globalsInit();
 
 uint64_t uplink_getTotalBytesReceived();
 
-bool uplink_init(dnbd3_image_t *image, int sock, dnbd3_host_t *host);
+bool uplink_init(dnbd3_image_t *image, int sock, dnbd3_host_t *host, int version);
 
 void uplink_removeClient(dnbd3_connection_t *uplink, dnbd3_client_t *client);
 
-bool uplink_request(dnbd3_client_t *client, uint64_t handle, uint64_t start, uint32_t length);
+bool uplink_request(dnbd3_client_t *client, uint64_t handle, uint64_t start, uint32_t length, uint8_t hopCount);
 
 void uplink_shutdown(dnbd3_image_t *image);