Restore original positions of bitfields in s2n_{config,connection}.h

Now that the positions of bitfields in structs are no longer important to SAW,
there is no reason to keep the bitfields in `s2n_config` and `s2n_connection`
up front, as was done in aws#3079. As a result, we can move the fields back to
their original positions before that commit.

tls/s2n_config.h

@@ -30,31 +30,18 @@
 struct s2n_cipher_preferences;
 
 struct s2n_config {
-    /* The following bitfield flags are used in SAW proofs. The positions of
-     * these flags are important, as SAW looks up each flag by their index
-     * in the struct starting from 0. See the comments surrounding
-     * config_bitfield in tests/saw/spec/handshake/handshake_io_lowlevel.saw for
-     * more details. Make sure that any new flags are added after these ones
-     * so that the indices in the SAW proofs do not need to be changed each time.
-     *
-     * START OF SAW-TRACKED BITFIELD FLAGS */
-
-    unsigned use_tickets:1;
-
-    /* Whether a connection can be used by a QUIC implementation.
-     * See s2n_quic_support.h */
-    unsigned quic_enabled:1;
-
-    /* END OF SAW-TRACKED BITFIELD FLAGS */
-
     unsigned cert_allocated:1;
     unsigned default_certs_are_explicit:1;
+    unsigned use_tickets:1;
     unsigned use_session_cache:1;
     /* if this is FALSE, server will ignore client's Maximum Fragment Length request */
     unsigned accept_mfl:1;
     unsigned check_ocsp:1;
     unsigned disable_x509_validation:1;
     unsigned max_verify_cert_chain_depth_set:1;
+    /* Whether a connection can be used by a QUIC implementation.
+     * See s2n_quic_support.h */
+    unsigned quic_enabled:1;
     /* Whether to add dss cert type during a server certificate request.
      * See https://github.com/aws/s2n-tls/blob/main/docs/USAGE-GUIDE.md */
     unsigned cert_req_dss_legacy_compat_enabled:1;

tls/s2n_connection.h

@@ -56,14 +56,26 @@ typedef enum {
 } s2n_session_ticket_status;
 
 struct s2n_connection {
-    /* The following bitfield flags are used in SAW proofs. The positions of
-     * these flags are important, as SAW looks up each flag by their index
-     * in the struct starting from 0. See the comments surrounding
-     * conn_bitfield in tests/saw/spec/handshake/handshake_io_lowlevel.saw for
-     * more details. Make sure that any new flags are added after these ones
-     * so that the indices in the SAW proofs do not need to be changed each time.
-     *
-     * START OF SAW-TRACKED BITFIELD FLAGS */
+    /* The configuration (cert, key .. etc ) */
+    struct s2n_config *config;
+
+    /* Overrides Security Policy in config if non-null */
+    const struct s2n_security_policy *security_policy_override;
+
+    /* The user defined context associated with connection */
+    void *context;
+
+    /* The user defined secret callback and context */
+    s2n_secret_cb secret_cb;
+    void *secret_cb_context;
+
+    /* The send and receive callbacks don't have to be the same (e.g. two pipes) */
+    s2n_send_fn *send;
+    s2n_recv_fn *recv;
+
+    /* The context passed to the I/O callbacks */
+    void *send_io_context;
+    void *recv_io_context;
 
     /* Is this connection using CORK/SO_RCVLOWAT optimizations? Only valid when the connection is using
      * managed_send_io
@@ -73,11 +85,6 @@ struct s2n_connection {
     /* Session resumption indicator on client side */
     unsigned client_session_resumed:1;
 
-    /* Connection can be used by a QUIC implementation */
-    unsigned quic_enabled:1;
-
-    /* END OF SAW-TRACKED BITFIELD FLAGS */
-
     /* Determines if we're currently sending or receiving in s2n_shutdown */
     unsigned close_notify_queued:1;
 
@@ -103,58 +110,6 @@ struct s2n_connection {
     /* If write fd is broken */
     unsigned write_fd_broken:1;
 
-    /* Has the user set their own I/O callbacks or is this connection using the
-     * default socket-based I/O set by s2n */
-    unsigned managed_send_io:1;
-    unsigned managed_recv_io:1;
-
-    /* Key update data */
-    unsigned key_update_pending:1;
-
-    /* Early data supported by caller.
-     * If a caller does not use any APIs that support early data,
-     * do not negotiate early data.
-     */
-    unsigned early_data_expected:1;
-
-    /* Connection overrides server_max_early_data_size */
-    unsigned server_max_early_data_size_overridden:1;
-
-    /* Connection overrides psk_mode.
-     * This means that the connection will keep the existing value of psk_params->type,
-     * even when setting a new config. */
-    unsigned psk_mode_overridden:1;
-
-    /* Have we received a close notify alert from the peer. */
-    unsigned close_notify_received:1;
-
-    /* Connection negotiated an EMS */
-    unsigned ems_negotiated:1;
-
-    /* Connection successfully set a ticket on the connection */
-    unsigned set_session:1;
-
-    /* The configuration (cert, key .. etc ) */
-    struct s2n_config *config;
-
-    /* Overrides Security Policy in config if non-null */
-    const struct s2n_security_policy *security_policy_override;
-
-    /* The user defined context associated with connection */
-    void *context;
-
-    /* The user defined secret callback and context */
-    s2n_secret_cb secret_cb;
-    void *secret_cb_context;
-
-    /* The send and receive callbacks don't have to be the same (e.g. two pipes) */
-    s2n_send_fn *send;
-    s2n_recv_fn *recv;
-
-    /* The context passed to the I/O callbacks */
-    void *send_io_context;
-    void *recv_io_context;
-
     /* Track request extensions to ensure correct response extension behavior.
      *
      * We need to track client and server extensions separately because some
@@ -367,6 +322,40 @@ struct s2n_connection {
     /* Cookie extension data */
     struct s2n_stuffer cookie_stuffer;
 
+    /* Has the user set their own I/O callbacks or is this connection using the
+     * default socket-based I/O set by s2n */
+    unsigned managed_send_io:1;
+    unsigned managed_recv_io:1;
+
+    /* Key update data */
+    unsigned key_update_pending:1;
+
+    /* Early data supported by caller.
+     * If a caller does not use any APIs that support early data,
+     * do not negotiate early data.
+     */
+    unsigned early_data_expected:1;
+
+    /* Connection overrides server_max_early_data_size */
+    unsigned server_max_early_data_size_overridden:1;
+
+    /* Connection overrides psk_mode.
+     * This means that the connection will keep the existing value of psk_params->type,
+     * even when setting a new config. */
+    unsigned psk_mode_overridden:1;
+
+    /* Have we received a close notify alert from the peer. */
+    unsigned close_notify_received:1;
+
+    /* Connection negotiated an EMS */
+    unsigned ems_negotiated:1;
+
+    /* Connection successfully set a ticket on the connection */
+    unsigned set_session:1;
+
+    /* Connection can be used by a QUIC implementation */
+    unsigned quic_enabled:1;
+
     /* Flags to prevent users from calling methods recursively.
      * This can be an easy mistake to make when implementing callbacks.
      */