refactor(core): migrate packet processing from pnet to smoltcp (#2456)

Replace pnet_packet parsing and mutation across gateway packet paths with the existing smoltcp wire APIs. Preserve length validation, fragmentation classification, TCP flags, and checksum behavior while removing the core pnet_packet feature dependency.
Reject stale non-initiator OSPF sync sessions: only initiator requests may create missing sessions, and a rejection clears the old initiator role only when the remote session generation is unchanged. This fixes an unbounded RPC storm caused by a delayed route sync recreating a session after both peers relinquished the initiator role, with regression tests for session creation and response reordering.

Cargo.lock

@@ -2345,7 +2345,7 @@ dependencies = [
  "paste",
  "percent-encoding",
  "pin-project-lite",
- "pnet",
+ "pnet_datalink",
  "prost 0.14.3",
  "quanta",
  "quinn",
@@ -2362,6 +2362,7 @@ dependencies = [
  "serial_test",
  "service-manager",
  "shellexpand",
+ "smoltcp",
  "socket2 0.5.10",
  "strum 0.27.2",
  "stun_codec",
@@ -2445,7 +2446,6 @@ dependencies = [
  "percent-encoding",
  "petgraph",
  "pin-project-lite",
- "pnet_packet",
  "prefix-trie",
  "prost 0.14.3",
  "prost-types 0.14.3",
@@ -2486,6 +2486,7 @@ dependencies = [
  "once_cell",
  "serde",
  "serde_json",
+ "thunk-rs",
  "tokio",
  "uuid",
 ]
@@ -6573,20 +6574,6 @@ dependencies = [
  "plotters-backend",
 ]
 
-[[package]]
-name = "pnet"
-version = "0.35.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "682396b533413cc2e009fbb48aadf93619a149d3e57defba19ff50ce0201bd0d"
-dependencies = [
- "ipnetwork",
- "pnet_base",
- "pnet_datalink",
- "pnet_packet",
- "pnet_sys",
- "pnet_transport",
-]
-
 [[package]]
 name = "pnet_base"
 version = "0.35.0"
@@ -6594,7 +6581,6 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "ffc190d4067df16af3aba49b3b74c469e611cad6314676eaf1157f31aa0fb2f7"
 dependencies = [
  "no-std-net",
- "serde",
 ]
 
 [[package]]
@@ -6607,43 +6593,9 @@ dependencies = [
  "libc",
  "pnet_base",
  "pnet_sys",
- "serde",
  "winapi",
 ]
 
-[[package]]
-name = "pnet_macros"
-version = "0.35.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "13325ac86ee1a80a480b0bc8e3d30c25d133616112bb16e86f712dcf8a71c863"
-dependencies = [
- "proc-macro2",
- "quote",
- "regex",
- "syn 2.0.117",
-]
-
-[[package]]
-name = "pnet_macros_support"
-version = "0.35.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "eed67a952585d509dd0003049b1fc56b982ac665c8299b124b90ea2bdb3134ab"
-dependencies = [
- "pnet_base",
-]
-
-[[package]]
-name = "pnet_packet"
-version = "0.35.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "4c96ebadfab635fcc23036ba30a7d33a80c39e8461b8bd7dc7bb186acb96560f"
-dependencies = [
- "glob",
- "pnet_base",
- "pnet_macros",
- "pnet_macros_support",
-]
-
 [[package]]
 name = "pnet_sys"
 version = "0.35.0"
@@ -6654,18 +6606,6 @@ dependencies = [
  "winapi",
 ]
 
-[[package]]
-name = "pnet_transport"
-version = "0.35.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "5f604d98bc2a6591cf719b58d3203fd882bdd6bf1db696c4ac97978e9f4776bf"
-dependencies = [
- "libc",
- "pnet_base",
- "pnet_packet",
- "pnet_sys",
-]
-
 [[package]]
 name = "png"
 version = "0.17.16"