Simon Law
28801674a6
The routecheck package parallels the netcheck package, where the former checks routes and routers while the latter checks networks. Like netcheck, it compiles reports for other systems to consume. Historically, the client has never known whether a peer is actually reachable. Most of the time this doesn’t matter, since the client will want to establish a WireGuard tunnel to any given destination. However, if the client needs to choose between two or more nodes, then it should try to choose a node that it can reach. Suggested exit nodes are one such example, where the client filters out any nodes that aren’t connected to the control plane. Sometimes an exit node will get disconnected from the control plane: when the network between the two is unreliable or when the exit node is too busy to keep its control connection alive. In these cases, Control disables the Node.Online flag for the exit node and broadcasts this across the tailnet. Arguably, the client should never have relied on this flag, since it only makes sense in the admin console. This patch implements an initial routecheck client that can probe every node that your client knows about. You should not ping scan your visible tailnet, this method is for debugging only. This patch also introduces a new OnNetMapToggle hook, which fires when the netmap transitions from nil to non-nil, or vice versa. This happens either when the client receives its first MapResponse after connecting to the control plane, or when it clears the netmap while it is disconnecting. Routecheck uses this to wait for a valid netmap so it knows which peers to probe. Updates #17366 Updates tailscale/corp#33033 Signed-off-by: Simon Law <sfllaw@tailscale.com>
52 lines
1.7 KiB
Go
52 lines
1.7 KiB
Go
// Copyright (c) Tailscale Inc & contributors
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// SPDX-License-Identifier: BSD-3-Clause
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package routecheck
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import (
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"net/netip"
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"tailscale.com/tailcfg"
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"tailscale.com/types/views"
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"tailscale.com/util/mak"
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)
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// RoutersByPrefix represents a map of nodes grouped by the subnet that they route.
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// Nodes that route for /0 prefixes are exit nodes, their subnet is the Internet.
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// The result omits any prefix that is one of a node’s local addresses.
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//
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// Note: Fallback routes are not supported by design. If a subnet prefix
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// contained within another more general prefix has no reachable routers,
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// traffic is still sent to one of those unreachable routers.
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// Routers for the general prefix aren’t candidates. See tailscale/tailscale#18550.
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type RoutersByPrefix map[netip.Prefix][]tailcfg.NodeView
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// RoutersByPrefix returns a map of nodes grouped by the subnet that they route.
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// See [RoutersByPrefix] for more detail.
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func (c *Client) RoutersByPrefix() RoutersByPrefix {
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var routers RoutersByPrefix
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for _, n := range c.nb.NodeBackend().Peers() {
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for _, pfx := range routes(n) {
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mak.Set(&routers, pfx, append(routers[pfx], n))
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}
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}
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return routers
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}
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// Routes returns a slice of subnets that the given node will route.
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// If the node is an exit node, the result will contain at least one /0 prefix.
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// If the node is a subnet router, the result will contain a smaller prefix.
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// The result omits any prefix that is one of the node’s local addresses.
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func routes(n tailcfg.NodeView) []netip.Prefix {
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var routes []netip.Prefix
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AllowedIPs:
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for _, pfx := range n.AllowedIPs().All() {
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// Routers never forward their own local addresses.
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if views.SliceContains(n.Addresses(), pfx) {
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continue AllowedIPs
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}
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routes = append(routes, pfx)
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}
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return routes
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}
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