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net/netcheck: fix crash when IPv6 kinda but not really works

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Looks like on some systems there's an IPv6 address, but then opening
a IPv6 UDP socket fails later. Probably some firewall. Tolerate it
better and don't crash.

To repro: check the "udp6" to something like "udp7" (something that'll
fail) and run "go run ./cmd/tailscale netcheck" on a machine with
active IPv6. It used to crash and now it doesn't.

Fixes #7949

Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
This commit is contained in:
Brad Fitzpatrick 2023-04-22 17:39:11 -07:00 committed by Brad Fitzpatrick
parent 7778d708a6
commit 90ba26cea1
1 changed files with 11 additions and 0 deletions
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11
net/netcheck/netcheck.go
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@ -40,6 +40,7 @@ import (
"tailscale.com/types/logger" "tailscale.com/types/logger"
"tailscale.com/types/nettype" "tailscale.com/types/nettype"
"tailscale.com/types/opt" "tailscale.com/types/opt"
"tailscale.com/types/ptr"
"tailscale.com/util/clientmetric" "tailscale.com/util/clientmetric"
"tailscale.com/util/mak" "tailscale.com/util/mak"
) )
@ -943,6 +944,16 @@ func (c *Client) GetReport(ctx context.Context, dm *tailcfg.DERPMap) (_ *Report,
go c.readPackets(ctx, u6) go c.readPackets(ctx, u6)
} }
} }
// If our interfaces.State suggested we have IPv6 support but then we
// failed to get an IPv6 sending socket (as in
// https://github.com/tailscale/tailscale/issues/7949), then change
// ifState.HaveV6 before we make a probe plan that involves sending IPv6
// packets and thus assuming rs.pc6 is non-nil.
if rs.pc6 == nil {
ifState = ptr.To(*ifState) // shallow clone
ifState.HaveV6 = false
}
} }
plan := makeProbePlan(dm, ifState, last) plan := makeProbePlan(dm, ifState, last)