[PATCH v6 nf-next 2/3] ipvs: tcp: enable per-connection secure_tcp in state machine

[Adriano Cordova <adrianox@gmail.com>]

Let set_tcp_state select tcp_states_dos when the connection
carries IP_VS_CONN_F_SECURE_TCP, otherwise keep using the
global pd->tcp_state_table (the netns default / or if nomem).

Signed-off-by: Adriano Cordova <adrianox@gmail.com>
---
Changes in v5:
- Document that secure_tcp is the netns-wide default and that a service
  can opt in to the hardened table with IP_VS_SVC_F_SECURE_TCP.

 Documentation/networking/ipvs-sysctl.rst |  4 ++++
 net/netfilter/ipvs/ip_vs_proto_tcp.c     | 16 +++++++++-------
 2 files changed, 13 insertions(+), 7 deletions(-)

diff --git a/Documentation/networking/ipvs-sysctl.rst b/Documentation/networking/ipvs-sysctl.rst
index fe36f4fcd3a0..5fc6afd2d39a 100644
--- a/Documentation/networking/ipvs-sysctl.rst
+++ b/Documentation/networking/ipvs-sysctl.rst
@@ -290,6 +290,10 @@ secure_tcp - INTEGER
 	The value definition is the same as that of drop_entry and
 	drop_packet.
 
+	This is the network-namespace default. A virtual service can opt
+	in to the hardened table regardless of this setting by setting
+	IP_VS_SVC_F_SECURE_TCP (0x0100) in its service flags.
+
 svc_lfactor - INTEGER
 	Possible values: -8 (larger table) .. 8 (smaller table)
 
diff --git a/net/netfilter/ipvs/ip_vs_proto_tcp.c b/net/netfilter/ipvs/ip_vs_proto_tcp.c
index fec0e8b47b71..3b9a2c8e9a52 100644
--- a/net/netfilter/ipvs/ip_vs_proto_tcp.c
+++ b/net/netfilter/ipvs/ip_vs_proto_tcp.c
@@ -451,11 +451,10 @@ static void tcp_timeout_change(struct ip_vs_proto_data *pd, int flags)
 	int on = (flags & 1);		/* secure_tcp */
 
 	/*
-	** FIXME: change secure_tcp to independent sysctl var
-	** or make it per-service or per-app because it is valid
-	** for most if not for all of the applications. Something
-	** like "capabilities" (flags) for each object.
-	*/
+	 * This remains the netns-wide default / global floor (e.g. when
+	 * memory pressure kicks in). Per-service hardening is now carried
+	 * by IP_VS_CONN_F_SECURE_TCP on each connection (set_tcp_state).
+	 */
 	pd->tcp_state_table = (on ? tcp_states_dos : tcp_states);
 }
 
@@ -479,6 +478,7 @@ set_tcp_state(struct ip_vs_proto_data *pd, struct ip_vs_conn *cp,
 	int state_idx;
 	int new_state = IP_VS_TCP_S_CLOSE;
 	int state_off = tcp_state_off[direction];
+	const struct tcp_states_t *table;
 
 	/*
 	 *    Update state offset to INPUT_ONLY if necessary
@@ -496,8 +496,10 @@ set_tcp_state(struct ip_vs_proto_data *pd, struct ip_vs_conn *cp,
 		goto tcp_state_out;
 	}
 
-	new_state =
-		pd->tcp_state_table[state_off+state_idx].next_state[cp->state];
+	table = pd->tcp_state_table;
+	if (cp->flags & IP_VS_CONN_F_SECURE_TCP)
+		table = tcp_states_dos;
+	new_state = table[state_off + state_idx].next_state[cp->state];
 
   tcp_state_out:
 	if (new_state != cp->state) {
-- 
2.51.0