Original file line numberDiff line numberDiff line change@@ -900,7 +900,9 @@ def has_dualstack_ipv6():
900900try:
901901withsocket(AF_INET6, SOCK_STREAM) assock:
902902sock.setsockopt(IPPROTO_IPV6, IPV6_V6ONLY, 0)
903-returnTrue
903+# On some platforms (e.g. DragonFly BSD) setting IPV6_V6ONLY to 0
904+# silently has no effect, so check that it was actually cleared.
905+returnsock.getsockopt(IPPROTO_IPV6, IPV6_V6ONLY) ==0
904906excepterror:
905907returnFalse
906908