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130 lines
3.3 KiB
Go
130 lines
3.3 KiB
Go
// Copyright (c) 2016-2017 Daniel Oaks <daniel@danieloaks.net>
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// released under the MIT license
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package connection_limits
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import (
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"errors"
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"fmt"
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"net"
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"sync"
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"github.com/oragono/oragono/irc/utils"
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)
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// LimiterConfig controls the automated connection limits.
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type LimiterConfig struct {
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Enabled bool
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CidrLenIPv4 int `yaml:"cidr-len-ipv4"`
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CidrLenIPv6 int `yaml:"cidr-len-ipv6"`
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ConnsPerSubnet int `yaml:"connections-per-subnet"`
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IPsPerSubnet int `yaml:"ips-per-subnet"` // legacy name for ConnsPerSubnet
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Exempted []string
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}
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var (
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errTooManyClients = errors.New("Too many clients in subnet")
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)
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// Limiter manages the automated client connection limits.
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type Limiter struct {
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sync.Mutex
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enabled bool
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ipv4Mask net.IPMask
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ipv6Mask net.IPMask
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// subnetLimit is the maximum number of clients per subnet
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subnetLimit int
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// population holds IP -> count of clients connected from there
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population map[string]int
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// exemptedNets holds networks that are exempt from limits
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exemptedNets []net.IPNet
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}
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// addrToKey canonicalizes `addr` to a string key.
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func addrToKey(addr net.IP, v4Mask net.IPMask, v6Mask net.IPMask) string {
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if addr.To4() != nil {
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addr = addr.Mask(v4Mask) // IP.Mask() handles the 4-in-6 mapping for us
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} else {
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addr = addr.Mask(v6Mask)
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}
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return addr.String()
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}
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// AddClient adds a client to our population if possible. If we can't, throws an error instead.
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// 'force' is used to add already-existing clients (i.e. ones that are already on the network).
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func (cl *Limiter) AddClient(addr net.IP, force bool) error {
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cl.Lock()
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defer cl.Unlock()
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if !cl.enabled {
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return nil
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}
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// check exempted lists
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// we don't track populations for exempted addresses or nets - this is by design
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if utils.IPInNets(addr, cl.exemptedNets) {
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return nil
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}
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// check population
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addrString := addrToKey(addr, cl.ipv4Mask, cl.ipv6Mask)
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if cl.population[addrString]+1 > cl.subnetLimit && !force {
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return errTooManyClients
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}
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cl.population[addrString] = cl.population[addrString] + 1
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return nil
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}
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// RemoveClient removes the given address from our population
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func (cl *Limiter) RemoveClient(addr net.IP) {
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cl.Lock()
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defer cl.Unlock()
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if !cl.enabled {
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return
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}
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addrString := addrToKey(addr, cl.ipv4Mask, cl.ipv6Mask)
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cl.population[addrString] = cl.population[addrString] - 1
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// safety limiter
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if cl.population[addrString] < 0 {
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cl.population[addrString] = 0
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}
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}
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// ApplyConfig atomically applies a config update to a connection limit handler
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func (cl *Limiter) ApplyConfig(config LimiterConfig) error {
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// assemble exempted nets
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exemptedNets, err := utils.ParseNetList(config.Exempted)
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if err != nil {
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return fmt.Errorf("Could not parse limiter exemption list: %v", err.Error())
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}
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cl.Lock()
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defer cl.Unlock()
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if cl.population == nil {
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cl.population = make(map[string]int)
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}
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cl.enabled = config.Enabled
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cl.ipv4Mask = net.CIDRMask(config.CidrLenIPv4, 32)
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cl.ipv6Mask = net.CIDRMask(config.CidrLenIPv6, 128)
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// subnetLimit is explicitly NOT capped at a minimum of one.
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// this is so that CL config can be used to allow ONLY clients from exempted IPs/nets
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cl.subnetLimit = config.ConnsPerSubnet
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// but: check if the current key was left unset, but the legacy was set:
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if cl.subnetLimit == 0 && config.IPsPerSubnet != 0 {
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cl.subnetLimit = config.IPsPerSubnet
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}
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cl.exemptedNets = exemptedNets
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return nil
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}
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