create separate irc/connection_limiting package

irc/connection_limits.go

@@ -1,144 +0,0 @@
-// Copyright (c) 2016-2017 Daniel Oaks <daniel@danieloaks.net>
-// released under the MIT license
-
-package irc
-
-import (
-	"errors"
-	"fmt"
-	"net"
-	"sync"
-)
-
-var (
-	errTooManyClients = errors.New("Too many clients in subnet")
-)
-
-// ConnectionLimits manages the automated client connection limits.
-type ConnectionLimits struct {
-	sync.Mutex
-
-	enabled  bool
-	ipv4Mask net.IPMask
-	ipv6Mask net.IPMask
-	// subnetLimit is the maximum number of clients per subnet
-	subnetLimit int
-	// population holds IP -> count of clients connected from there
-	population map[string]int
-
-	// exemptedIPs holds IPs that are exempt from limits
-	exemptedIPs map[string]bool
-	// exemptedNets holds networks that are exempt from limits
-	exemptedNets []net.IPNet
-}
-
-// maskAddr masks the given IPv4/6 address with our cidr limit masks.
-func (cl *ConnectionLimits) maskAddr(addr net.IP) net.IP {
-	if addr.To4() == nil {
-		// IPv6 addr
-		addr = addr.Mask(cl.ipv6Mask)
-	} else {
-		// IPv4 addr
-		addr = addr.Mask(cl.ipv4Mask)
-	}
-
-	return addr
-}
-
-// AddClient adds a client to our population if possible. If we can't, throws an error instead.
-// 'force' is used to add already-existing clients (i.e. ones that are already on the network).
-func (cl *ConnectionLimits) AddClient(addr net.IP, force bool) error {
-	cl.Lock()
-	defer cl.Unlock()
-
-	if !cl.enabled {
-		return nil
-	}
-
-	// check exempted lists
-	// we don't track populations for exempted addresses or nets - this is by design
-	if cl.exemptedIPs[addr.String()] {
-		return nil
-	}
-	for _, ex := range cl.exemptedNets {
-		if ex.Contains(addr) {
-			return nil
-		}
-	}
-
-	// check population
-	cl.maskAddr(addr)
-	addrString := addr.String()
-
-	if cl.population[addrString]+1 > cl.subnetLimit && !force {
-		return errTooManyClients
-	}
-
-	cl.population[addrString] = cl.population[addrString] + 1
-
-	return nil
-}
-
-// RemoveClient removes the given address from our population
-func (cl *ConnectionLimits) RemoveClient(addr net.IP) {
-	cl.Lock()
-	defer cl.Unlock()
-
-	if !cl.enabled {
-		return
-	}
-
-	addrString := addr.String()
-	cl.population[addrString] = cl.population[addrString] - 1
-
-	// safety limiter
-	if cl.population[addrString] < 0 {
-		cl.population[addrString] = 0
-	}
-}
-
-// NewConnectionLimits returns a new connection limit handler.
-// The handler is functional, but disabled; it can be enabled via `ApplyConfig`.
-func NewConnectionLimits() *ConnectionLimits {
-	var cl ConnectionLimits
-
-	// initialize empty population; all other state is configurable
-	cl.population = make(map[string]int)
-
-	return &cl
-}
-
-// ApplyConfig atomically applies a config update to a connection limit handler
-func (cl *ConnectionLimits) ApplyConfig(config ConnectionLimitsConfig) error {
-	// assemble exempted nets
-	exemptedIPs := make(map[string]bool)
-	var exemptedNets []net.IPNet
-	for _, cidr := range config.Exempted {
-		ipaddr := net.ParseIP(cidr)
-		_, netaddr, err := net.ParseCIDR(cidr)
-
-		if ipaddr == nil && err != nil {
-			return fmt.Errorf("Could not parse exempted IP/network [%s]", cidr)
-		}
-
-		if ipaddr != nil {
-			exemptedIPs[ipaddr.String()] = true
-		} else {
-			exemptedNets = append(exemptedNets, *netaddr)
-		}
-	}
-
-	cl.Lock()
-	defer cl.Unlock()
-
-	cl.enabled = config.Enabled
-	cl.ipv4Mask = net.CIDRMask(config.CidrLenIPv4, 32)
-	cl.ipv6Mask = net.CIDRMask(config.CidrLenIPv6, 128)
-	// subnetLimit is explicitly NOT capped at a minimum of one.
-	// this is so that CL config can be used to allow ONLY clients from exempted IPs/nets
-	cl.subnetLimit = config.IPsPerCidr
-	cl.exemptedIPs = exemptedIPs
-	cl.exemptedNets = exemptedNets
-
-	return nil
-}