111 lines
3.4 KiB
Go
111 lines
3.4 KiB
Go
// Copyright (c) Tailscale Inc & AUTHORS
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// SPDX-License-Identifier: BSD-3-Clause
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//go:build linux
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package linuxfw
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import (
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"tailscale.com/envknob"
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"tailscale.com/hostinfo"
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"tailscale.com/types/logger"
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"tailscale.com/version/distro"
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)
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func detectFirewallMode(logf logger.Logf) FirewallMode {
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if distro.Get() == distro.Gokrazy {
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// Reduce startup logging on gokrazy. There's no way to do iptables on
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// gokrazy anyway.
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logf("GoKrazy should use nftables.")
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hostinfo.SetFirewallMode("nft-gokrazy")
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return FirewallModeNfTables
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}
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envMode := envknob.String("TS_DEBUG_FIREWALL_MODE")
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// We now use iptables as default and have "auto" and "nftables" as
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// options for people to test further.
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switch envMode {
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case "auto":
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return pickFirewallModeFromInstalledRules(logf, linuxFWDetector{})
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case "nftables":
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logf("envknob TS_DEBUG_FIREWALL_MODE=nftables set")
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hostinfo.SetFirewallMode("nft-forced")
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return FirewallModeNfTables
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case "iptables":
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logf("envknob TS_DEBUG_FIREWALL_MODE=iptables set")
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hostinfo.SetFirewallMode("ipt-forced")
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default:
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logf("default choosing iptables")
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hostinfo.SetFirewallMode("ipt-default")
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}
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return FirewallModeIPTables
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}
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// tableDetector abstracts helpers to detect the firewall mode.
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// It is implemented for testing purposes.
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type tableDetector interface {
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iptDetect() (int, error)
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nftDetect() (int, error)
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}
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type linuxFWDetector struct{}
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// iptDetect returns the number of iptables rules in the current namespace.
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func (l linuxFWDetector) iptDetect() (int, error) {
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return detectIptables()
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}
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// nftDetect returns the number of nftables rules in the current namespace.
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func (l linuxFWDetector) nftDetect() (int, error) {
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return detectNetfilter()
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}
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// pickFirewallModeFromInstalledRules returns the firewall mode to use based on
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// the environment and the system's capabilities.
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func pickFirewallModeFromInstalledRules(logf logger.Logf, det tableDetector) FirewallMode {
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if distro.Get() == distro.Gokrazy {
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// Reduce startup logging on gokrazy. There's no way to do iptables on
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// gokrazy anyway.
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return FirewallModeNfTables
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}
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iptAva, nftAva := true, true
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iptRuleCount, err := det.iptDetect()
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if err != nil {
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logf("detect iptables rule: %v", err)
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iptAva = false
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}
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nftRuleCount, err := det.nftDetect()
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if err != nil {
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logf("detect nftables rule: %v", err)
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nftAva = false
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}
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logf("nftables rule count: %d, iptables rule count: %d", nftRuleCount, iptRuleCount)
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switch {
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case nftRuleCount > 0 && iptRuleCount == 0:
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logf("nftables is currently in use")
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hostinfo.SetFirewallMode("nft-inuse")
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return FirewallModeNfTables
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case iptRuleCount > 0 && nftRuleCount == 0:
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logf("iptables is currently in use")
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hostinfo.SetFirewallMode("ipt-inuse")
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return FirewallModeIPTables
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case nftAva:
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// if both iptables and nftables are available but
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// neither/both are currently used, use nftables.
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logf("nftables is available")
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hostinfo.SetFirewallMode("nft")
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return FirewallModeNfTables
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case iptAva:
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logf("iptables is available")
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hostinfo.SetFirewallMode("ipt")
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return FirewallModeIPTables
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default:
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// if neither iptables nor nftables are available, use iptablesRunner as a dummy
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// runner which exists but won't do anything. Creating iptablesRunner errors only
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// if the iptables command is missing or doesn’t support "--version", as long as it
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// can determine a version then it’ll carry on.
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hostinfo.SetFirewallMode("ipt-fb")
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return FirewallModeIPTables
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}
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}
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