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// Package userip provides functions for extracting a user IP address from a
// request and associating it with a Context.
//
// This package is an example to accompany https://blog.golang.org/context.
// It is not intended for use by others.
package userip
import (
"fmt"
"net"
"net/http"
"golang.org/x/net/context"
)
// FromRequest extracts the user IP address from req, if present.
func FromRequest(req *http.Request) (net.IP, error) {
ip, _, err := net.SplitHostPort(req.RemoteAddr)
if err != nil {
return nil, fmt.Errorf("userip: %q is not IP:port", req.RemoteAddr)
}
userIP := net.ParseIP(ip)
if userIP == nil {
return nil, fmt.Errorf("userip: %q is not IP:port", req.RemoteAddr)
}
return userIP, nil
}
// The key type is unexported to prevent collisions with context keys defined in
// other packages.
type key int
// userIPkey is the context key for the user IP address. Its value of zero is
// arbitrary. If this package defined other context keys, they would have
// different integer values.
const userIPKey key = 0
// NewContext returns a new Context carrying userIP.
func NewContext(ctx context.Context, userIP net.IP) context.Context {
return context.WithValue(ctx, userIPKey, userIP)
}
// FromContext extracts the user IP address from ctx, if present.
func FromContext(ctx context.Context) (net.IP, bool) {
// ctx.Value returns nil if ctx has no value for the key;
// the net.IP type assertion returns ok=false for nil.
userIP, ok := ctx.Value(userIPKey).(net.IP)
return userIP, ok
}
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