From: Mateusz Poliwczak <mpoliwczak34@gmail.com>
Date: Tue, 20 Dec 2022 15:24:06 +0000 (+0000)
Subject: net: use correct dns msg size
X-Git-Tag: go1.20rc2~1^2~17
X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=78fc81070a853d08a71f70fa20b2093f5535e6c5;p=gostls13.git

net: use correct dns msg size

Set bufSize to the actual dns message size, so that the p.Start (below) gets a fully valid dns message.

Change-Id: I585e8a3d71f88db93e09bd0dbbc0875ee6de9a97
GitHub-Last-Rev: 0967be35012d2e28366e6d47eee4968c7e8d5e4a
GitHub-Pull-Request: golang/go#57392
Reviewed-on: https://go-review.googlesource.com/c/go/+/458375
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Ian Lance Taylor <iant@google.com>
Auto-Submit: Ian Lance Taylor <iant@google.com>
Reviewed-by: Damien Neil <dneil@google.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
---

diff --git a/src/net/cgo_unix.go b/src/net/cgo_unix.go
index 5b0df56eae..6a2c369c66 100644
--- a/src/net/cgo_unix.go
+++ b/src/net/cgo_unix.go
@@ -383,8 +383,9 @@ func cgoResSearch(hostname string, rtype, class int) ([]dnsmessage.Resource, err
 	s := _C_CString(hostname)
 	defer _C_FreeCString(s)
 
+	var size int
 	for {
-		size, _ := _C_res_nsearch(state, s, class, rtype, buf, bufSize)
+		size, _ = _C_res_nsearch(state, s, class, rtype, buf, bufSize)
 		if size <= 0 || size > 0xffff {
 			return nil, errors.New("res_nsearch failure")
 		}
@@ -399,7 +400,7 @@ func cgoResSearch(hostname string, rtype, class int) ([]dnsmessage.Resource, err
 	}
 
 	var p dnsmessage.Parser
-	if _, err := p.Start(unsafe.Slice((*byte)(unsafe.Pointer(buf)), bufSize)); err != nil {
+	if _, err := p.Start(unsafe.Slice((*byte)(unsafe.Pointer(buf)), size)); err != nil {
 		return nil, err
 	}
 	p.SkipAllQuestions()