Initial Commit

.editorconfig

@@ -0,0 +1,15 @@
+# EditorConfig is awesome: https://EditorConfig.org
+
+# top-most EditorConfig file
+root = true
+
+[*]
+indent_style = space
+indent_size = 2
+end_of_line = lf
+charset = utf-8
+trim_trailing_whitespace = true
+insert_final_newline = false
+
+[Makefile]
+indent_style = tab

.gitignore

@@ -0,0 +1 @@
+getpsrc

.golangci.yml

@@ -0,0 +1,28 @@
+run:
+  skip-dirs:
+  - it
+  timeout: 10m
+  tests: true
+
+linters:
+  disable-all: true
+  enable:
+  # Default
+  - deadcode
+  - errcheck
+  - gosimple
+  - govet
+  - ineffassign
+  - staticcheck
+  - structcheck
+  - typecheck
+  - unused
+  - varcheck
+
+  # Additionally linters
+  - bodyclose
+  - misspell
+  - nilerr
+  - rowserrcheck
+  - sqlclosecheck
+  - unparam

Dockerfile

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+ARG BASE_IMAGE
+ARG BUILD_IMAGE
+
+# BUILD
+# =====================================================================
+FROM ${BUILD_IMAGE} AS build
+
+ARG GONOPROXY
+ARG GONOSUMDB
+ARG GOPRIVATE
+ARG GOPROXY
+ARG GOSUMDB
+ARG VERSION
+
+COPY ./ /workspace
+
+RUN cd /workspace && \
+    GONOPROXY=${GONOPROXY} \
+    GONOSUMDB=${GONOSUMDB} \
+    GOPRIVATE=${GOPRIVATE} \
+    GOPROXY=${GOPROXY} \
+    GOSUMDB=${GOSUMDB} \
+    VERSION=${VERSION} \
+      make all
+
+# TARGET
+# =====================================================================
+FROM ${BASE_IMAGE}
+
+COPY --from=build /workspace/getpsrc /usr/bin/getpsrc
+
+ENTRYPOINT [ "/usr/bin/getpsrc" ]

LICENSE

@@ -0,0 +1,13 @@
+Copyright 2019 Markus Pesch
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.

Makefile

@@ -0,0 +1,126 @@
+# VERSION
+VERSION?=$(shell git describe --abbrev=0)+hash.$(shell git rev-parse --short HEAD)
+
+# CONTAINER_RUNTIME
+CONTAINER_RUNTIME?=$(shell which docker)
+
+# BUILD_IMAGE
+BUILD_IMAGE_REGISTRY_HOST?=docker.io
+BUILD_IMAGE_NAMESPACE=library
+BUILD_IMAGE_REPOSITORY=golang
+BUILD_IMAGE_VERSION?=1.16
+BUILD_IMAGE_FULLY_QUALIFIED:=${BUILD_IMAGE_REGISTRY_HOST}/${BUILD_IMAGE_NAMESPACE}/${BUILD_IMAGE_REPOSITORY}:${BUILD_IMAGE_VERSION}
+
+# BASE_IMAGE
+BASE_IMAGE_REGISTRY_HOST?=docker.io
+BASE_IMAGE_NAMESPACE=library
+BASE_IMAGE_REPOSITORY=busybox
+BASE_IMAGE_VERSION?=latest
+BASE_IMAGE_FULLY_QUALIFIED=${BASE_IMAGE_REGISTRY_HOST}/${BASE_IMAGE_NAMESPACE}/${BASE_IMAGE_REPOSITORY}:${BASE_IMAGE_VERSION}
+
+# CONTAINER_IMAGE
+CONTAINER_IMAGE_REGISTRY_HOST?=docker.io
+CONTAINER_IMAGE_NAMESPACE=volkerraschek
+CONTAINER_IMAGE_REPOSITORY=getpsrc
+CONTAINER_IMAGE_VERSION?=latest
+CONTAINER_IMAGE_FULLY_QUALIFIED=${CONTAINER_IMAGE_REGISTRY_HOST}/${CONTAINER_IMAGE_NAMESPACE}/${CONTAINER_IMAGE_REPOSITORY}:${CONTAINER_IMAGE_VERSION}
+CONTAINER_IMAGE_UNQUALIFIED=${CONTAINER_IMAGE_NAMESPACE}/${CONTAINER_IMAGE_REPOSITORY}:${CONTAINER_IMAGE_VERSION}
+
+# EXECUTABLES
+# ==============================================================================
+EXECUTABLE_TARGETS=getpsrc
+
+PHONY=all
+all: clean ${EXECUTABLE_TARGETS}
+
+getpsrc:
+	GOPRIVATE=$(shell go env GOPRIVATE) \
+	GOPROXY=$(shell go env GOPROXY) \
+	GONOPROXY=$(shell go env GONOPROXY) \
+	GONOSUMDB=$(shell go env GONOSUMDB) \
+	GOSUMDB=$(shell go env GOSUMDB) \
+		go build -tags netgo -ldflags "-X main.version=${VERSION}" -o ${@} main.go
+
+# CLEAN
+# ==============================================================================
+PHONY+=clean
+clean:
+	rm --force --recursive $(shell pwd)/getpsrc*
+
+# GOLANGCI-LINT
+# ==============================================================================
+PHONY+=golangci-lint
+golangci-lint:
+	golangci-lint run --concurrency=$(shell nproc)
+
+# GOSEC
+# ==============================================================================
+PHONY+=gosec
+gosec:
+	gosec $(shell pwd)/...
+
+# CONTAINER-IMAGE
+# ==============================================================================
+PHONY+=container-image/build
+container-image/build:
+	${CONTAINER_RUNTIME} build \
+		--build-arg BASE_IMAGE=${BASE_IMAGE_FULLY_QUALIFIED} \
+		--build-arg BUILD_IMAGE=${BUILD_IMAGE_FULLY_QUALIFIED} \
+		--build-arg GOPRIVATE=$(shell go env GOPRIVATE) \
+		--build-arg GOPROXY=$(shell go env GOPROXY) \
+		--build-arg GONOPROXY=$(shell go env GONOPROXY) \
+		--build-arg GONOSUMDB=$(shell go env GONOSUMDB) \
+		--build-arg GOSUMDB=$(shell go env GOSUMDB) \
+		--build-arg VERSION=${VERSION} \
+		--file ./Dockerfile \
+		--no-cache \
+		--tag ${CONTAINER_IMAGE_UNQUALIFIED} \
+		--tag ${CONTAINER_IMAGE_FULLY_QUALIFIED} \
+		.
+
+PHONY+=container-image/push
+container-image/push: container-image/build
+	${CONTAINER_RUNTIME} push ${CONTAINER_IMAGE_FULLY_QUALIFIED}
+
+# CONTAINER STEPS - EXECUTABLE
+# ==============================================================================
+PHONY+=container-run/all
+container-run/all:
+	$(MAKE) container-run COMMAND=${@:container-run/%=%}
+
+PHONY+=${EXECUTABLE_TARGETS:%=container-run/%}
+${EXECUTABLE_TARGETS:%=container-run/%}:
+	$(MAKE) container-run COMMAND=${@:container-run/%=%}
+
+# CONTAINER STEPS - CLEAN
+# ==============================================================================
+PHONY+=container-run/clean
+container-run/clean:
+	$(MAKE) container-run COMMAND=${@:container-run/%=%}
+
+# GENERAL CONTAINER COMMAND
+# ==============================================================================
+PHONY+=container-run
+container-run:
+	${CONTAINER_RUNTIME} run \
+		--env CONTAINER_IMAGE_VERSION=${CONTAINER_IMAGE_VERSION} \
+		--env GONOPROXY=$(shell go env GONOPROXY) \
+		--env GONOSUMDB=$(shell go env GONOSUMDB) \
+		--env GOPRIVATE=$(shell go env GOPRIVATE) \
+		--env GOPROXY=$(shell go env GOPROXY) \
+		--env GOSUMDB=$(shell go env GOSUMDB) \
+		--env VERSION=${VERSION} \
+		--net=host \
+		--rm \
+		--volume /tmp:/tmp \
+		--volume ${HOME}/go:/root/go \
+		--volume $(shell pwd):/workspace \
+		--workdir /workspace \
+			${BUILD_IMAGE_FULLY_QUALIFIED} \
+				make ${COMMAND}
+
+# PHONY
+# ==============================================================================
+# Declare the contents of the PHONY variable as phony. We keep that information
+# in a variable so we can use it in if_changed.
+.PHONY: ${PHONY}

README.md

@@ -0,0 +1,7 @@
+# getpsrc
+
+`getpsrc` is a small programme to determine the src routing ip for an external ip.
+
+`getpsrc` serves as an alternative to `ip route get <ip> | awk ... ` because `ip
+route get` can return different output depending on the environment and
+therefore the construct is unsafe.

go.mod

@@ -0,0 +1,5 @@
+module github.com/volker-raschek/getpsrc
+
+go 1.16
+
+require github.com/google/gopacket v1.1.20-0.20210429153827-3eaba0894325

go.sum

@@ -0,0 +1,21 @@
+github.com/google/gopacket v1.1.19 h1:ves8RnFZPGiFnTS0uPQStjwru6uO6h+nlr9j6fL7kF8=
+github.com/google/gopacket v1.1.19/go.mod h1:iJ8V8n6KS+z2U1A8pUwu8bW5SyEMkXJB8Yo/Vo+TKTo=
+github.com/google/gopacket v1.1.20-0.20210429153827-3eaba0894325 h1:YmIcZ5Var3BAQ64AW98Iiys5Ih4fiU0xK41+8isC5Ec=
+github.com/google/gopacket v1.1.20-0.20210429153827-3eaba0894325/go.mod h1:riddUzxTSBpJXk3qBHtYr4qOhFhT6k/1c0E3qkQjQpA=
+github.com/vishvananda/netlink v1.1.0/go.mod h1:cTgwzPIzzgDAYoQrMm0EdrjRUBkTqKYppBueQtXaqoE=
+github.com/vishvananda/netns v0.0.0-20191106174202-0a2b9b5464df/go.mod h1:JP3t17pCcGlemwknint6hfoeCVQrEMVwxRLRjXpq+BU=
+github.com/vishvananda/netns v0.0.0-20210104183010-2eb08e3e575f/go.mod h1:DD4vA1DwXk04H54A1oHXtwZmA0grkVMdPxx/VGLCah0=
+golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
+golang.org/x/crypto v0.0.0-20191011191535-87dc89f01550/go.mod h1:yigFU9vqHzYiE8UmvKecakEJjdnWj3jj499lnFckfCI=
+golang.org/x/lint v0.0.0-20200302205851-738671d3881b/go.mod h1:3xt1FjdF8hUf6vQPIChWIBhFzV8gjjsPE/fR3IyQdNY=
+golang.org/x/mod v0.1.1-0.20191105210325-c90efee705ee/go.mod h1:QqPTAvyqsEbceGzBzNggFXnrqF1CaUcvgkdR5Ot7KZg=
+golang.org/x/net v0.0.0-20190404232315-eb5bcb51f2a3/go.mod h1:t9HGtf8HONx5eT2rtn7q6eTqICYqUVnKs3thJo3Qplg=
+golang.org/x/net v0.0.0-20190620200207-3b0461eec859/go.mod h1:z5CRVTTTmAJ677TzLLGU+0bjPO0LkuOLi4/5GtJWs/s=
+golang.org/x/sync v0.0.0-20190423024810-112230192c58/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
+golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
+golang.org/x/sys v0.0.0-20190412213103-97732733099d/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/sys v0.0.0-20190606203320-7fc4e5ec1444/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/sys v0.0.0-20200217220822-9197077df867/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
+golang.org/x/tools v0.0.0-20200130002326-2f3ba24bd6e7/go.mod h1:TB2adYChydJhpapKDTa4BR/hXlZSLoq2Wpct/0txZ28=
+golang.org/x/xerrors v0.0.0-20191011141410-1b5146add898/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=

main.go

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+package main
+
+import (
+	"fmt"
+	"log"
+	"net"
+	"os"
+	"strings"
+
+	"github.com/google/gopacket/routing"
+)
+
+func main() {
+	ips := os.Args[1:]
+	switch {
+	case len(ips) == 0:
+		log.Fatal("Expect exactly one argument")
+	case len(ips) >= 2:
+		log.Fatal("Expect only one argument")
+	}
+
+	rawIP := strings.Split(ips[0], "/")[0]
+
+	ip := net.ParseIP(rawIP)
+	if ip == nil {
+		log.Fatal("failed to parse raw ip")
+	}
+
+	router, err := routing.New()
+	if err != nil {
+		log.Fatalf("failed to get new routing instance: %v", err.Error())
+	}
+
+	_, _, prefferedSrc, err := router.Route(ip)
+	if err != nil {
+		log.Fatalf("failed to find gateway for ip: %v", err.Error())
+	}
+
+	fmt.Fprintln(os.Stdout, prefferedSrc.String())
+}