refactor: move code from src to root dir

.github/actions/install-dependencies/action.yaml

@@ -6,10 +6,10 @@ runs:
   using: composite
   steps:
     - name: Setup Go
-      uses: actions/setup-go@c4a742cab115ed795e34d4513e2cf7d472deb55f
+      uses: actions/setup-go@0c52d547c9bc32b1aa3301fd7a9cb496313a4491
       with:
-        go-version-file: src/go.mod
-        cache-dependency-path: src/go.sum
+        go-version-file: go.mod
+        cache-dependency-path: go.sum
         cache: true
     - name: Install Compilers & Formatters
       shell: bash

.github/workflows/verify-pr.yaml

@@ -7,7 +7,8 @@ concurrency:
 
 on:
   pull_request:
-    branches: [ "main" ]
+    branches:
+      - main
 
 jobs:
   verify:
@@ -22,8 +23,8 @@ jobs:
 
     - name: Compile App
       run: |
-        make -C src
+        make
 
     - name: Run App
       run: |
-        sudo timeout --preserve-status 5s ./src/socket-filter
+        sudo timeout --preserve-status 5s ./socket-filter

.gitignore

@@ -1 +1,6 @@
-.idea/
+.idea/
+
+.output/
+
+socket-filter
+socket-filter.bpf.o

src/Makefile → Makefile

@@ -6,16 +6,16 @@ CLANG_FORMAT ?= clang-format
 LLVM_STRIP ?= llvm-strip
 GO ?= go
 
-LIBBPF_SRC := $(abspath ../libbpf/src)
+LIBBPF_SRC := $(abspath ./libbpf/src)
 LIBBPF_OBJ := $(abspath $(OUTPUT)/libbpf.a)
 
-BPFTOOL_SRC := $(abspath ../bpftool/src)
+BPFTOOL_SRC := $(abspath ./bpftool/src)
 BPFTOOL_OUTPUT ?= $(abspath $(OUTPUT)/bpftool)
 BPFTOOL ?= $(BPFTOOL_OUTPUT)/bootstrap/bpftool
 
 ARCH ?= $(shell uname -m | sed 's/x86_64/x86/' | sed 's/aarch64/arm64/')
 BTFFILE = /sys/kernel/btf/vmlinux
-VMLINUX := ../vmlinux/$(ARCH)/vmlinux.h
+VMLINUX := ./vmlinux/$(ARCH)/vmlinux.h
 
 # Use our own libbpf API headers and Linux UAPI headers distributed with
 # libbpf to avoid dependency on system-wide headers, which could be missing or
@@ -29,38 +29,38 @@ all: socket-filter
 
 .PHONY: clean
 clean:
-	$(Q)rm -rf $(OUTPUT) socket-filter.bpf.o socket-filter
+	rm -rf $(OUTPUT) socket-filter.bpf.o socket-filter
 
 $(OUTPUT) $(OUTPUT)/libbpf $(BPFTOOL_OUTPUT):
-	$(Q)mkdir -p $@
+	mkdir -p $@
 
 # Build libbpf
 $(LIBBPF_OBJ): $(wildcard $(LIBBPF_SRC)/*.[ch] $(LIBBPF_SRC)/Makefile) | $(OUTPUT)/libbpf
-	$(Q)$(MAKE) -C $(LIBBPF_SRC) BUILD_STATIC_ONLY=1 \
+	$(MAKE) -C $(LIBBPF_SRC) BUILD_STATIC_ONLY=1 \
 		OBJDIR=$(dir $@)/libbpf DESTDIR=$(dir $@)    \
 		INCLUDEDIR= LIBDIR= UAPIDIR=                 \
 		install
 
 # Build bpftool
 $(BPFTOOL): | $(BPFTOOL_OUTPUT)
-	$(Q)$(MAKE) ARCH= CROSS_COMPILE= OUTPUT=$(BPFTOOL_OUTPUT)/ -C $(BPFTOOL_SRC) bootstrap
+	$(MAKE) ARCH= CROSS_COMPILE= OUTPUT=$(BPFTOOL_OUTPUT)/ -C $(BPFTOOL_SRC) bootstrap
 
 # Build BPF code
 socket-filter.bpf.o: socket-filter.bpf.c $(LIBBPF_OBJ) | $(OUTPUT)
-	$(Q)$(CLANG) -g -O2 -target bpf -D__TARGET_ARCH_$(ARCH) $(INCLUDES) $(CLANG_BPF_SYS_INCLUDES) -c socket-filter.bpf.c -o $@
-	$(Q)$(LLVM_STRIP) -g $@
+	$(CLANG) -g -O2 -target bpf -D__TARGET_ARCH_$(ARCH) $(INCLUDES) $(CLANG_BPF_SYS_INCLUDES) -c socket-filter.bpf.c -o $@
+	$(LLVM_STRIP) -g $@
 
 # Build application binary
 socket-filter: socket-filter.bpf.o main.go
-	$(Q)$(GO) build -o $@ main.go
+	$(GO) build -o $@ main.go
 
 .PHONY: $(VMLINUX)
 $(VMLINUX): $(BPFTOOL)
-	$(Q)$(BPFTOOL) btf dump file $(BTFFILE) format c > $(VMLINUX)
+	$(BPFTOOL) btf dump file $(BTFFILE) format c > $(VMLINUX)
 
 .PHONY: format
 format:
-	$(Q)$(CLANG_FORMAT) --verbose -i \
+	$(CLANG_FORMAT) --verbose -i \
 	socket-filter.bpf.c \
 	socket-filter.h
 

README.md

@@ -3,6 +3,15 @@
 The `socket-filter` program demonstrates how to load an eBPF program from an ELF file,
 and attach it to a raw socket.
 
+`BPF_PROG_TYPE_SOCKET_FILTER` was the first program type to be added to the
+Linux kernel. When you attach a BPF program to a raw socket, you get access to
+all the packets processed by that socket. Socket filter programs don't allow
+you to modify the contents of those packets or to change the destination for
+those packets; they give you access to them for observability purposes only.
+The metadata that your program receives contains information related to the
+network stack such as the protocol type that's being used to deliver the
+packet.
+
 ## Usage
 
 Clone and change current directory to the cloned repository:
@@ -20,13 +29,13 @@ git submodule update --init --recursive
 Compile BPF application and Go loader:
 
 ```
-make -C src all
+make
 ```
 
 Run the application:
 
 ``` console
-$ sudo ./src/socket-filter --index=0
+$ sudo ./socket-filter --index=0
 Filtering on eth index: 0
         ICMP: 20 TCP: 121 UDP: 12_
 ```

src/socket-filter.bpf.c → socket-filter.bpf.c

@@ -1,10 +1,10 @@
 //+build ignore
 
+#include "socket-filter.h"
 #include "vmlinux.h"
 #include <bpf/bpf_core_read.h>
 #include <bpf/bpf_helpers.h>
 #include <bpf/bpf_tracing.h>
-#include "socket-filter.h"
 
 char LICENSE[] SEC("license") = "GPL";