flow_dissector: set encapsulated control flags from tun_flags

Set the new FLOW_DIS_F_TUNNEL_* encapsulated control flags, based
on if their counter-part is set in tun_flags.

These flags are not userspace visible yet, as the code to dump
encapsulated control flags will first be added, and later activated
in the following patches.

Signed-off-by: Asbjørn Sloth Tønnesen <ast@fiberby.net>
Tested-by: Davide Caratti <dcaratti@redhat.com>
Reviewed-by: Davide Caratti <dcaratti@redhat.com>
Link: https://patch.msgid.link/20240713021911.1631517-8-ast@fiberby.net
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: Asbjørn Sloth Tønnesen

net/core/flow_dissector.c

@@ -396,6 +396,15 @@ skb_flow_dissect_tunnel_info(const struct sk_buff *skb,
 
 	key = &info->key;
 
+	if (test_bit(IP_TUNNEL_CSUM_BIT, key->tun_flags))
+		ctrl_flags |= FLOW_DIS_F_TUNNEL_CSUM;
+	if (test_bit(IP_TUNNEL_DONT_FRAGMENT_BIT, key->tun_flags))
+		ctrl_flags |= FLOW_DIS_F_TUNNEL_DONT_FRAGMENT;
+	if (test_bit(IP_TUNNEL_OAM_BIT, key->tun_flags))
+		ctrl_flags |= FLOW_DIS_F_TUNNEL_OAM;
+	if (test_bit(IP_TUNNEL_CRIT_OPT_BIT, key->tun_flags))
+		ctrl_flags |= FLOW_DIS_F_TUNNEL_CRIT_OPT;
+
 	switch (ip_tunnel_info_af(info)) {
 	case AF_INET:
 		skb_flow_dissect_set_enc_control(FLOW_DISSECTOR_KEY_IPV4_ADDRS,