feat: add synproxy statement and list object

also mark some other statements that are missing.
compare with nftables json_parse_stmt:  https://git.netfilter.org/nftables/tree/src/parser_json.c?id=c4c740117f6fbf39dd67dd87635ea8b497718ad7#n2884

src/schema.rs

@@ -42,6 +42,7 @@ pub enum NfListObject {
     CTTimeout(CTTimeout),
     #[serde(rename = "ct expectation")]
     CTExpectation(CTExpectation),
+    SynProxy(SynProxy),
 }
 
 #[derive(Clone, Debug, Eq, PartialEq, Serialize, Deserialize)]
@@ -435,3 +436,31 @@ pub struct CTExpectation {
     #[serde(skip_serializing_if = "Option::is_none")]
     pub size: Option<u32>,
 }
+
+/// [SynProxy] intercepts new TCP connections and handles the initial 3-way handshake using
+/// syncookies instead of conntrack to establish the connection.
+///
+/// Named SynProxy requires **nftables 0.9.3 or newer**.
+///
+/// [SynProxy]: https://wiki.nftables.org/wiki-nftables/index.php/Synproxy
+#[derive(Debug, Clone, Eq, PartialEq, Serialize, Deserialize)]
+pub struct SynProxy {
+    /// The table’s family.
+    pub family: NfFamily,
+    /// The table’s name.
+    pub table: String,
+    /// The synproxy's name.
+    pub name: String,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    /// The synproxy's handle. For input, it is used by the [delete command][NfCmd::Delete] only.
+    pub handle: Option<u32>,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    /// The maximum segment size (must match your backend server).
+    pub mss: Option<u16>,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    /// The window scale (must match your backend server).
+    pub wscale: Option<u8>,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    /// The synproxy's [flags][crate::types::SynProxyFlag].
+    pub flags: Option<HashSet<SynProxyFlag>>,
+}

src/stmt.rs

@@ -4,7 +4,7 @@ use serde::{Deserialize, Serialize};
 
 use strum_macros::EnumString;
 
-use crate::types::RejectCode;
+use crate::types::{RejectCode, SynProxyFlag};
 use crate::visitor::single_string_to_option_hashset_logflag;
 
 use crate::expr::Expression;
@@ -36,8 +36,10 @@ pub enum Statement {
     #[serde(rename = "quota")]
     /// reference to a named quota object
     QuotaRef(String),
+    // TODO: last
     Limit(Limit),
 
+    // TODO: flow
     FWD(Option<FWD>),
     /// Disable connection tracking for the packet.
     Notrack,
@@ -48,6 +50,7 @@ pub enum Statement {
     Redirect(Option<NAT>),   // redirect is subset of NAT options
     Reject(Option<Reject>),
     Set(Set),
+    // TODO: map
     Log(Option<Log>),
 
     #[serde(rename = "ct helper")]
@@ -57,6 +60,7 @@ pub enum Statement {
     Meter(Meter),
     Queue(Queue),
     #[serde(rename = "vmap")]
+    // TODO: vmap is expr, not stmt!
     VerdictMap(VerdictMap),
 
     #[serde(rename = "ct count")]
@@ -73,9 +77,12 @@ pub enum Statement {
     /// This represents an xt statement from xtables compat interface.
     /// Sadly, at this point, it is not possible to provide any further information about its content.
     XT(Option<serde_json::Value>),
-
+    /// A netfilter synproxy intercepts new TCP connections and handles the initial 3-way handshake using syncookies instead of conntrack to establish the connection.
+    SynProxy(SynProxy),
     /// Redirects the packet to a local socket without changing the packet header in any way.
     TProxy(TProxy),
+    // TODO: reset
+    // TODO: secmark
 }
 
 #[derive(Debug, Clone, Eq, PartialEq, Serialize, Deserialize)]
@@ -432,6 +439,22 @@ pub struct CTCount {
     pub inv: Option<bool>,
 }
 
+#[derive(Debug, Clone, Eq, PartialEq, Serialize, Deserialize)]
+/// Limit the number of connections using conntrack.
+/// 
+/// Anonymous synproxy was requires **nftables 0.9.2 or newer**.
+pub struct SynProxy {
+    #[serde(skip_serializing_if = "Option::is_none")]
+    /// maximum segment size (must match your backend server)
+    pub mss: Option<u32>,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    /// window scale (must match your backend server)
+    pub wscale: Option<u32>,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    /// The synproxy's [flags][crate::types::SynProxyFlag].
+    pub flags: Option<HashSet<SynProxyFlag>>,
+}
+
 #[derive(Debug, Clone, Eq, PartialEq, Serialize, Deserialize)]
 #[serde(rename_all = "lowercase")]
 /// Redirects the packet to a local socket without changing the packet header in any way.

src/types.rs

@@ -90,3 +90,14 @@ pub enum RejectCode {
     /// Address unreachable (ICMPv6)
     AddrUnreach,
 }
+
+#[derive(Clone, Debug, Eq, PartialEq, Serialize, Deserialize, Hash)]
+#[serde(rename_all = "lowercase")]
+/// Describes a SynProxy's flags.
+pub enum SynProxyFlag {
+    /// Pass client timestamp option to backend.
+    Timestamp,
+    #[serde(rename = "sack-perm")]
+    /// Pass client selective acknowledgement option to backend.
+    SackPerm,
+}