restore: networking stack files from reflog (Phases 1-6)

Recovered from reflog commits 1c80937e and d0ecc067 after force-push data loss.
Includes: filter/, icmp_error.rs, slaac.rs, bond.rs, bridge.rs, gre.rs, ipip.rs,
qdisc.rs, tun.rs, vlan.rs, vxlan.rs, netfilter.rs, tun.rs, conntrack.rs, nat.rs,
rule.rs, table.rs, redbear-ufw/, dhcpv6d/, netdiag/ — 39 files total.

netstack/src/icmp_error.rs

@@ -0,0 +1,116 @@
+//! ICMP error message generation — mirrors Linux 7.1's `icmp_send`.
+//!
+//! Reference files:
+//! - `net/ipv4/icmp.c:802` — `__icmp_send()` — builds ICMPv4 error messages
+//! - `net/ipv6/icmp.c:icmpv6_send()` — ICMPv6 error messages
+//! - `include/uapi/linux/icmp.h` — ICMP type/code constants
+//!
+//! ICMP error messages contain: ICMP header + original IP header + 8 bytes
+//! of original transport payload (RFC 792 §3.1, RFC 4443 §2.4).
+
+use smoltcp::wire::{
+    Icmpv4Packet, Icmpv4Repr, Icmpv6Packet, Icmpv6Repr, IpAddress, Ipv4Address, Ipv4Packet,
+    Ipv4Repr, Ipv6Address, Ipv6Packet, Ipv6Repr,
+};
+
+/// Builds an ICMPv4 Destination Unreachable error message (Type 3).
+/// Code 3 = Port Unreachable (mirrors `ICMP_PORT_UNREACH` in icmp.c).
+pub fn build_icmpv4_port_unreachable(
+    original_packet: &[u8],
+) -> Option<Vec<u8>> {
+    let ipv4 = Ipv4Packet::new_checked(original_packet).ok()?;
+    let src = ipv4.src_addr();
+    let dst = ipv4.dst_addr();
+
+    let ip_header_len = (ipv4.version() & 0x0f) as usize * 4;
+    let total_len = original_packet.len().min(ip_header_len + 8);
+
+    let mut payload = alloc::vec![0u8; 4 + total_len];
+    payload[0] = 0;
+    payload[1] = 0;
+    payload[2] = 0;
+    payload[3] = 0;
+    payload[4..4 + total_len].copy_from_slice(&original_packet[..total_len]);
+
+    let icmp_repr = Icmpv4Repr::DstUnreachable {
+        reason: smoltcp::wire::Icmpv4DstUnreachable::PortUnreachable,
+        header: Ipv4Repr {
+            src_addr: dst,
+            dst_addr: src,
+            next_header: smoltcp::wire::IpProtocol::Icmp,
+            hop_limit: 64,
+            payload_len: 4 + total_len,
+        },
+        data: &payload,
+    };
+
+    let mut buf = alloc::vec![0u8; icmp_repr.buffer_len()];
+    let mut pkt = Icmpv4Packet::new_unchecked(&mut buf);
+    icmp_repr.emit(&mut pkt, &smoltcp::phy::ChecksumCapabilities::ignored());
+    Some(buf)
+}
+
+/// Builds an ICMPv4 Time Exceeded error message (Type 11, Code 0).
+/// Mirrors `ICMP_TIME_EXCEEDED` / `ICMP_EXC_TTL` in `icmp.c:1168`.
+pub fn build_icmpv4_time_exceeded(
+    original_packet: &[u8],
+) -> Option<Vec<u8>> {
+    let ipv4 = Ipv4Packet::new_checked(original_packet).ok()?;
+    let src = ipv4.src_addr();
+    let dst = ipv4.dst_addr();
+
+    let ip_header_len = (ipv4.version() & 0x0f) as usize * 4;
+    let total_len = original_packet.len().min(ip_header_len + 8);
+
+    let mut payload = alloc::vec![0u8; 4 + total_len];
+    payload[4..4 + total_len].copy_from_slice(&original_packet[..total_len]);
+
+    let icmp_repr = Icmpv4Repr::TimeExceeded {
+        reason: smoltcp::wire::Icmpv4TimeExceeded::TtlExpired,
+        header: Ipv4Repr {
+            src_addr: dst,
+            dst_addr: src,
+            next_header: smoltcp::wire::IpProtocol::Icmp,
+            hop_limit: 64,
+            payload_len: 4 + total_len,
+        },
+        data: &payload,
+    };
+
+    let mut buf = alloc::vec![0u8; icmp_repr.buffer_len()];
+    let mut pkt = Icmpv4Packet::new_unchecked(&mut buf);
+    icmp_repr.emit(&mut pkt, &smoltcp::phy::ChecksumCapabilities::ignored());
+    Some(buf)
+}
+
+/// Builds an ICMPv6 Destination Unreachable error (Type 1, Code 4).
+pub fn build_icmpv6_port_unreachable(
+    original_packet: &[u8],
+) -> Option<Vec<u8>> {
+    let ipv6 = Ipv6Packet::new_checked(original_packet).ok()?;
+    let src = ipv6.src_addr();
+    let _dst = ipv6.dst_addr();
+
+    let total_len = original_packet.len().min(48);
+    let mut data = alloc::vec![0u8; 4 + total_len];
+    data[4..4 + total_len].copy_from_slice(&original_packet[..total_len]);
+
+    let icmp_repr = Icmpv6Repr::DstUnreachable {
+        reason: smoltcp::wire::Icmpv6DstUnreachable::PortUnreachable,
+        header: Ipv6Repr {
+            src_addr: _dst,
+            dst_addr: src,
+            next_header: smoltcp::wire::IpProtocol::Icmpv6,
+            hop_limit: 64,
+            payload_len: 4 + total_len,
+        },
+        data: &data,
+    };
+
+    let mut buf = alloc::vec![0u8; icmp_repr.buffer_len()];
+    let mut pkt = Icmpv6Packet::new_unchecked(&mut buf);
+    icmp_repr.emit(&_dst, &src, &mut pkt, &smoltcp::phy::ChecksumCapabilities::ignored());
+    Some(buf)
+}
+
+extern crate alloc;