[SERVER] iscsi refactor: First working version

Work towards simplifying the iscsi implementation has begun. Goals are:
- Simpler and easier to understand resource/lifecycle management of
  allocations
- Single-threaded architecture, making locking unnecessary
- Moving as many allocations as possible to the stack
- Making the call-stack more shallow for easier tracking of code flow

1 files changed, 60 insertions, 0 deletions

diff --git a/src/server/sendfile.c b/src/server/sendfile.c
new file mode 100644
index 0000000..9e27238
--- /dev/null
+++ b/src/server/sendfile.c
@@ -0,0 +1,60 @@
+#include "sendfile.h"
+
+#if defined(__linux__)
+#include <sys/sendfile.h>
+#elif defined(__FreeBSD__)
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <sys/uio.h>
+#else
+#error "What platform is this?"
+#endif
+
+#include <errno.h>
+
+bool sendfile_all(const int fd, const int sock, off_t foffset, const size_t bytes)
+{
+	if ( bytes == 0 )
+		return true;
+#ifdef DNBD3_SERVER_AFL
+	errno = 0;
+	return true;
+#elif defined(__linux__)
+	size_t done = 0;
+	int againCount = 0;
+
+	while ( done < bytes ) {
+		const ssize_t sent = sendfile( sock, fd, &foffset, bytes - done );
+		if ( sent == 0 ) // Probably EOF, like with send(), but manpage is not clear :-/
+			return false;
+		if ( sent < 0 ) {
+			if ( errno == EAGAIN || errno == EINTR ) {
+				// Retry once, but give up otherwise - EAGAIN might just be the send timeout
+				if ( ++againCount > 1 )
+					return false;
+				continue;
+			}
+			return false;
+		}
+		done += sent;
+	}
+#elif defined(__FreeBSD__)
+	off_t sent;
+	size_t done = 0;
+	int againCount = 0;
+
+	while ( done < bytes ) {
+		const int ret = sendfile( fd, sock, foffset + done, bytes - done, NULL, &sent, 0 );
+		if ( ret == 0 || errno == EAGAIN || errno == EINTR ) {
+			// Retry once, but give up otherwise - EAGAIN might just be the send timeout
+			if ( sent == 0 && ++againCount > 1 )
+				return false;
+			done += sent;
+			continue;
+		}
+		// Something else went wrong
+		return false;
+	}
+#endif
+	return true;
+}
\ No newline at end of file