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ddtrace/tracer: Ensure SpanLink access is safe from corruption #2975

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merged 3 commits into from
Nov 14, 2024
Merged

ddtrace/tracer: Ensure SpanLink access is safe from corruption #2975

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739cd86
safegaurd and cleanup
mtoffl01 Nov 11, 2024
bf2289d
Add interface check
mtoffl01 Nov 11, 2024
a7a8a7a
Merge branch 'main' into mtoff/safeguard-spanlinks
mtoffl01 Nov 14, 2024
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5 changes: 1 addition & 4 deletions ddtrace/ddtrace.go
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Original file line number Diff line number Diff line change
Expand Up @@ -38,11 +38,8 @@ type SpanContextW3C interface {
type SpanContextWithLinks interface {
SpanContext

// SpanLinks returns the span links on the SpanContext.
// SpanLinks returns a copy of the span links on the SpanContext.
SpanLinks() []SpanLink

// Setlinks takes in a slice of SpanLinks and sets them to the SpanContext.
SetLinks(links []SpanLink)
}

// Tracer specifies an implementation of the Datadog tracer which allows starting
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10 changes: 4 additions & 6 deletions ddtrace/tracer/context_test.go
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Expand Up @@ -84,14 +84,12 @@ func TestStartSpanWithSpanLinks(t *testing.T) {
_, _, _, stop := startTestTracer(t)
defer stop()
spanLink := ddtrace.SpanLink{TraceID: 789, TraceIDHigh: 0, SpanID: 789, Attributes: map[string]string{"reason": "terminated_context", "context_headers": "datadog"}, Flags: 0}
var ctx ddtrace.SpanContext
ctx = &spanContext{spanID: 789, traceID: traceIDFrom64Bits(789), spanLinks: []ddtrace.SpanLink{spanLink}}
ctx := &spanContext{spanID: 789, traceID: traceIDFrom64Bits(789), spanLinks: []ddtrace.SpanLink{spanLink}}

t.Run("spanContext with spanLinks satisfies SpanContextWithLinks interface", func(t *testing.T) {
ctxLink, ok := ctx.(ddtrace.SpanContextWithLinks)
assert.True(t, ok)
assert.Equal(t, len(ctxLink.SpanLinks()), 1)
assert.Equal(t, ctxLink.SpanLinks()[0], spanLink)
var _ ddtrace.SpanContextWithLinks = ctx
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Should an assertion be made here to make sure that the casting doesn't fail? Otherwise what is the point of this declaration? 🤔

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@mtoffl01 mtoffl01 Nov 11, 2024 •
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The code won't compile if this fails; this is a common code pattern for "checking that a concrete type fulfills an interface" in Go.
https://dev.to/kittipat1413/checking-if-a-type-satisfies-an-interface-in-go-432n#:~:text=In%20Go%2C%20to%20check%20if,now%2C%20not%20at%20runtime.%E2%80%9D

assert.Equal(t, len(ctx.SpanLinks()), 1)
assert.Equal(t, ctx.SpanLinks()[0], spanLink)
})

t.Run("create span from spancontext with links", func(t *testing.T) {
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9 changes: 4 additions & 5 deletions ddtrace/tracer/spancontext.go
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Expand Up @@ -183,12 +183,11 @@ func (c *spanContext) TraceID128Bytes() [16]byte {
return c.traceID
}

// SpanLinks implements ddtrace.SpanContextWithLinks
func (c *spanContext) SpanLinks() []ddtrace.SpanLink {
return c.spanLinks
}

func (c *spanContext) SetLinks(links []ddtrace.SpanLink) {
c.spanLinks = links
cp := make([]ddtrace.SpanLink, len(c.spanLinks))
copy(cp, c.spanLinks)
return cp
}

// ForeachBaggageItem implements ddtrace.SpanContext.
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