conn: fix cmsg data padding calculation for gso

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

diff --git a/conn/gso_linux.go b/conn/gso_linux.go
index b8599ce0b44acded9bce415d2d21916ebc037d66..8596b292eca0bc590da273ae0069648a7ede3de2 100644 (file)
--- a/conn/gso_linux.go
+++ b/conn/gso_linux.go
@@ -56,7 +56,7 @@ func setGSOSize(control *[]byte, gsoSize uint16) {
        hdr.Level = unix.SOL_UDP
        hdr.Type = unix.UDP_SEGMENT
        hdr.SetLen(unix.CmsgLen(sizeOfGSOData))
-       copy((gsoControl)[unix.SizeofCmsghdr:], unsafe.Slice((*byte)(unsafe.Pointer(&gsoSize)), sizeOfGSOData))
+       copy((gsoControl)[unix.CmsgLen(0):], unsafe.Slice((*byte)(unsafe.Pointer(&gsoSize)), sizeOfGSOData))
        *control = (*control)[:existingLen+space]
 }