fix: remove vmlinux crate dep (#28)

* fix: remove vmlinux crate dep

* fix: download architecture-specific vmlinux.h at build time

Instead of using a git dependency (not allowed on crates.io), download the
architecture-specific vmlinux.h header at build time from the libbpf/vmlinux.h
repository. This approach:

- Removes git dependency from Cargo.toml (crates.io compatible)
- Downloads correct arch-specific header (x86, aarch64, arm)
- Caches downloaded headers in OUT_DIR (reuses between builds)
- Works with cargo install
- Supports cross-compilation for all architectures

The vmlinux.h file (~3-4MB per arch) is downloaded once per architecture
and cached, so subsequent builds are fast.

* fix: use ureq with rustls instead of http_req

http_req depends on native-tls/openssl-sys which requires OpenSSL to be
installed in the cross-compilation containers. Switch to ureq with the
rustls backend which has no system dependencies and works in all
cross-compilation environments.

* fix: follow symlink when downloading vmlinux.h

The vmlinux.h files in the libbpf/vmlinux.h repository are symlinks to
versioned files (e.g. vmlinux_6.14.h). When downloading via
raw.githubusercontent.com, we get the symlink content (just the target
filename) instead of the actual file.

Solution: Download the symlink first to get the target filename, then
download the actual versioned file. This ensures we get the full header
content instead of just the symlink text.

* add crate publish workflow

.github/workflows/docker.yml

@@ -1,27 +1,8 @@
 name: Docker Build and Publish
-
 on:
   push:
-    branches: [ "main" ]
-    paths:
-      - 'src/**'
-      - 'Cargo.toml'
-      - 'Cargo.lock'
-      - 'assets/services'
-      - 'Dockerfile'
-      - 'build.rs'
-      - '.github/workflows/docker.yml'
-    tags: [ "v*.*.*" ]
-  pull_request:
-    branches: [ "main" ]
-    paths:
-      - 'src/**'
-      - 'Cargo.toml'
-      - 'Cargo.lock'
-      - 'assets/services'
-      - 'Dockerfile'
-      - 'build.rs'
-      - '.github/workflows/docker.yml'
+    tags:
+      - "v[0-9]+.[0-9]+.[0-9]+"
   workflow_dispatch:
 
 env:

.github/workflows/publish.yml

@@ -0,0 +1,23 @@
+name: Publish to crates.io
+
+on:
+  push:
+    tags:
+      - "v[0-9]+.[0-9]+.[0-9]+"
+  workflow_dispatch:
+
+jobs:
+  publish:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+
+      - name: Set up Rust
+        uses: dtolnay/rust-toolchain@stable
+
+      - name: Publish to crates.io
+        env:
+          CARGO_REGISTRY_TOKEN: ${{ secrets.CRATES_IO_TOKEN }}
+        run: cargo publish

.github/workflows/release.yml

@@ -86,9 +86,7 @@ jobs:
 
       - name: Install cross
         if: matrix.cargo == 'cross'
-        uses: taiki-e/cache-cargo-install-action@v2
-        with:
-          tool: cross@0.2.5
+        run: cargo install cross@0.2.5
 
       - name: Build release binary
         shell: bash