Overhauled SSL to use explicit BIO buffers

luprex/cpp/drv/driver-linux.cpp

@@ -149,40 +149,42 @@ static SOCKET accept_on_socket(SOCKET listen_socket, std::string &err) {
     }
 }
 
-// the return values for socket_send and socket_recv are:
+// the return values for socket_send:
 //
-//  positive: sent or received bytes successfully
-//  zero: would block
-//  negative: channel closed, possibly cleanly or possibly with error
+//  positive: sent bytes successfully
+//  negative: error.
+//     If the error message is empty, then it's "would block"
+//     Any other error generates an error message.
 //
 static int socket_send(SOCKET socket, const char *bytes, int nbytes, std::string &err) {
-    err.clear();
     int wbytes = send(socket, bytes, nbytes, 0);
     if (wbytes < 0) {
         if ((errno == EAGAIN) || (errno == EWOULDBLOCK)) {
-            return 0;
+            err.clear();
         } else {
             err = drvutil::strerror_str(errno);
-            return -1;
         }
+        return -1;
     } else {
+        err.clear();
         return wbytes;
     }
 }
 
 static int socket_recv(SOCKET socket, char *bytes, int nbytes, std::string &err) {
-    err.clear();
     int nrecv = recv(socket, bytes, nbytes, 0);
     if (nrecv < 0) {
-        if ((errno == EWOULDBLOCK) || (errno == EAGAIN)) {
-            err = drvutil::strerror_str(errno);
-            return -1;
+        if ((errno == EAGAIN) || (errno == EWOULDBLOCK)) {
+            err.clear();
         } else {
-            return 0;
+            err = drvutil::strerror_str(errno);
         }
-    } else if (nrecv == 0) {
         return -1;
+    } else if (nrecv == 0) {
+        err.clear();
+        return 0;
     } else {
+        err.clear();
         return nrecv;
     }
 }