init

.dockerignore

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+/.git
+/ip

.gitignore

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+/.git
+/ip

Dockerfile

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+FROM docker.io/golang:1.23.0 AS builder
+
+WORKDIR /app
+
+COPY . .
+
+RUN make
+
+FROM alpine:latest
+
+WORKDIR /app
+
+COPY --from=builder /app/ip .
+
+EXPOSE 8080
+
+CMD ["/app/ip"]

Makefile

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+.PHONY: linux
+linux:
+	CGO_ENABLED=0 go build -v -ldflags '-extldflags=-static'

README.md

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+# ip tool
+
+the simplest ip tool
+
+usage:
+
+```bash
+curl http://yourservice:8080/
+```

go.mod

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+module ip
+
+go 1.23.0

main.go

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+package main
+
+import (
+	"flag"
+	"log"
+	"net/http"
+	"strconv"
+)
+
+func main() {
+	port := flag.Int("port", 8080, "port to listen on")
+	flag.Parse()
+
+	mux := http.NewServeMux()
+	mux.HandleFunc("/", IPHandler)
+
+	log.Println("Listening on port", *port)
+	http.ListenAndServe(":"+strconv.Itoa(*port), mux)
+}
+
+func IPHandler(w http.ResponseWriter, r *http.Request) {
+	addr := r.RemoteAddr
+
+	w.Write([]byte(addr))
+	w.Write([]byte("\n"))
+
+	if r.Header.Get("X-Real-IP") != "" {
+		w.Write([]byte("X-Real-IP: "))
+		w.Write([]byte(r.Header.Get("X-Real-IP")))
+		w.Write([]byte("\n"))
+	}
+
+	if r.Header.Get("X-Forwarded-For") != "" {
+		w.Write([]byte("X-Forwarded-For: "))
+		w.Write([]byte(r.Header.Get("X-Forwarded-For")))
+		w.Write([]byte("\n"))
+	}
+}