Detect when disconnected

Sometimes when a connection is closed unceremoniously we cannot tell
until we try to read. This allows us to set an error the rest of the
library will understand so that the disconnect is properly detected.

Author: singpolyma

src/tls_openssl.c

@@ -19,6 +19,7 @@
 
 #ifndef _WIN32
 #include <sys/select.h>
+#include <sys/socket.h>
 #else
 #include <winsock2.h>
 #endif
@@ -963,6 +964,17 @@ int tls_read(struct conn_interface *intf, void *buff, size_t len)
     ret = SSL_read(tls->ssl, buff, len);
     _tls_set_error(tls, ret <= 0 ? SSL_get_error(tls->ssl, ret) : 0);
 
+#ifndef _WIN32
+    if (tls->lasterror == SSL_ERROR_WANT_READ) {
+        char c;
+        ssize_t n = recv(intf->conn->sock, &c, 1, MSG_PEEK);
+        if (n < 0 && errno == ENOTCONN) {
+            strophe_debug(tls->ctx, "tls", "WANT_READ but connection is closed");
+            _tls_set_error(tls, SSL_ERROR_SYSCALL); // Set a more appropriate error
+        }
+    }
+#endif
+
     return ret;
 }