net/http: fix HTTP/2 idle pool tracing

CL 140357 caused HTTP/2 connections to be put in the idle pool, but
failed to properly guard the trace.GotConn call in getConn. dialConn
returns a minimal persistConn with conn == nil for HTTP/2 connections.
This persistConn was then returned from queueForIdleConn and caused the
httptrace.GotConnInfo passed into GotConn to have a nil Conn field.

HTTP/2 connections call GotConn themselves so leave it for HTTP/2 to call
GotConn as is done directly below.

Fixes #34282

Change-Id: If54bfaf6edb14f5391463f908efbef5bb8a5d78e
GitHub-Last-Rev: 2b7d66a1ce66b4424c4d0fca2b8e8b547d874136
GitHub-Pull-Request: golang/go#34283
Reviewed-on: https://go-review.googlesource.com/c/go/+/195237
Reviewed-by: Michael Fraenkel <michael.fraenkel@gmail.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

1 files changed, 24 insertions, 0 deletions

diff --git a/src/net/http/export_test.go b/src/net/http/export_test.go
index d265cd3f72..e5c06a8903 100644
--- a/src/net/http/export_test.go
+++ b/src/net/http/export_test.go
@@ -208,6 +208,30 @@ func (t *Transport) PutIdleTestConn(scheme, addr string) bool {
 	}) == nil
 }
 
+// PutIdleTestConnH2 reports whether it was able to insert a fresh
+// HTTP/2 persistConn for scheme, addr into the idle connection pool.
+func (t *Transport) PutIdleTestConnH2(scheme, addr string, alt RoundTripper) bool {
+	key := connectMethodKey{"", scheme, addr, false}
+
+	if t.MaxConnsPerHost > 0 {
+		// Transport is tracking conns-per-host.
+		// Increment connection count to account
+		// for new persistConn created below.
+		t.connsPerHostMu.Lock()
+		if t.connsPerHost == nil {
+			t.connsPerHost = make(map[connectMethodKey]int)
+		}
+		t.connsPerHost[key]++
+		t.connsPerHostMu.Unlock()
+	}
+
+	return t.tryPutIdleConn(&persistConn{
+		t:        t,
+		alt:      alt,
+		cacheKey: key,
+	}) == nil
+}
+
 // All test hooks must be non-nil so they can be called directly,
 // but the tests use nil to mean hook disabled.
 func unnilTestHook(f *func()) {