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wgengine/magicsock: prefer private endpoints to public ones

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Switch our best address selection to use a scoring-based approach, where
we boost each address based on whether it's a private IP or IPv6.

For users in cloud environments, this biases endpoint selection towards
using an endpoint that is less likely to cost the user money, and should
be less surprising to users.

This also involves updating the tests to not use private IPv4 addresses;
other than that change, the behaviour should be identical for existing
endpoints.

Updates #8097

Signed-off-by: Andrew Dunham <andrew@du.nham.ca>
Change-Id: I069e3b399daea28be66b81f7e44fc27b2943d8af
This commit is contained in:
Andrew Dunham
2023-05-08 09:55:14 -04:00
parent eefee6f149
commit 2a9d46c38f
2 changed files with 109 additions and 42 deletions
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87
wgengine/magicsock/magicsock_test.go
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@ -1631,52 +1631,101 @@ func TestBetterAddr(t *testing.T) {
return addrLatency{netip.MustParseAddrPort(ipps), d}
}
zero := addrLatency{}
const (
publicV4 = "1.2.3.4:555"
publicV4_2 = "5.6.7.8:999"
publicV6 = "[2001::5]:123"
privateV4 = "10.0.0.2:123"
)
tests := []struct {
a, b addrLatency
want bool
want bool // whether a is better than b
}{
{a: zero, b: zero, want: false},
{a: al("10.0.0.2:123", 5*ms), b: zero, want: true},
{a: zero, b: al("10.0.0.2:123", 5*ms), want: false},
{a: al("10.0.0.2:123", 5*ms), b: al("1.2.3.4:555", 10*ms), want: true},
{a: al("10.0.0.2:123", 5*ms), b: al("10.0.0.2:123", 10*ms), want: false}, // same IPPort
{a: al(publicV4, 5*ms), b: zero, want: true},
{a: zero, b: al(publicV4, 5*ms), want: false},
{a: al(publicV4, 5*ms), b: al(publicV4_2, 10*ms), want: true},
{a: al(publicV4, 5*ms), b: al(publicV4, 10*ms), want: false}, // same IPPort
// Don't prefer b to a if it's not substantially better.
{a: al("10.0.0.2:123", 100*ms), b: al("1.2.3.4:555", 101*ms), want: false},
{a: al("10.0.0.2:123", 100*ms), b: al("1.2.3.4:555", 103*ms), want: true},
{a: al(publicV4, 100*ms), b: al(publicV4_2, 100*ms), want: false},
{a: al(publicV4, 100*ms), b: al(publicV4_2, 101*ms), want: false},
{a: al(publicV4, 100*ms), b: al(publicV4_2, 103*ms), want: true},
// Prefer IPv6 if roughly equivalent:
// Latencies of zero don't result in a divide-by-zero
{a: al(publicV4, 0), b: al(publicV4_2, 0), want: false},
// Prefer private IPs to public IPs if roughly equivalent...
{
a: al("[2001::5]:123", 100*ms),
b: al("1.2.3.4:555", 91*ms),
a: al(privateV4, 100*ms),
b: al(publicV4, 91*ms),
want: true,
},
{
a: al("1.2.3.4:555", 91*ms),
b: al("[2001::5]:123", 100*ms),
a: al(publicV4, 91*ms),
b: al(privateV4, 100*ms),
want: false,
},
// ... but not if the private IP is slower.
{
a: al(privateV4, 100*ms),
b: al(publicV4, 30*ms),
want: false,
},
{
a: al(publicV4, 30*ms),
b: al(privateV4, 100*ms),
want: true,
},
// Prefer IPv6 if roughly equivalent:
{
a: al(publicV6, 100*ms),
b: al(publicV4, 91*ms),
want: true,
},
{
a: al(publicV4, 91*ms),
b: al(publicV6, 100*ms),
want: false,
},
// But not if IPv4 is much faster:
{
a: al("[2001::5]:123", 100*ms),
b: al("1.2.3.4:555", 30*ms),
a: al(publicV6, 100*ms),
b: al(publicV4, 30*ms),
want: false,
},
{
a: al("1.2.3.4:555", 30*ms),
b: al("[2001::5]:123", 100*ms),
a: al(publicV4, 30*ms),
b: al(publicV6, 100*ms),
want: true,
},
// Private IPs are preferred over public IPs even if the public
// IP is IPv6.
{
a: al("192.168.0.1:555", 100*ms),
b: al("[2001::5]:123", 101*ms),
want: true,
},
{
a: al("[2001::5]:123", 101*ms),
b: al("192.168.0.1:555", 100*ms),
want: false,
},
}
for _, tt := range tests {
for i, tt := range tests {
got := betterAddr(tt.a, tt.b)
if got != tt.want {
t.Errorf("betterAddr(%+v, %+v) = %v; want %v", tt.a, tt.b, got, tt.want)
t.Errorf("[%d] betterAddr(%+v, %+v) = %v; want %v", i, tt.a, tt.b, got, tt.want)
continue
}
gotBack := betterAddr(tt.b, tt.a)
if got && gotBack {
t.Errorf("betterAddr(%+v, %+v) and betterAddr(%+v, %+v) both unexpectedly true", tt.a, tt.b, tt.b, tt.a)
t.Errorf("[%d] betterAddr(%+v, %+v) and betterAddr(%+v, %+v) both unexpectedly true", i, tt.a, tt.b, tt.b, tt.a)
}
}