From nobody Wed Nov 24 02:08:39 2021 X-Original-To: freebsd-net@mlmmj.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mlmmj.nyi.freebsd.org (Postfix) with ESMTP id EF2A21894590 for ; Wed, 24 Nov 2021 02:08:48 +0000 (UTC) (envelope-from jschauma@netmeister.org) Received: from panix.netmeister.org (panix.netmeister.org [166.84.7.99]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id 4HzPZ80BTZz4b58 for ; Wed, 24 Nov 2021 02:08:47 +0000 (UTC) (envelope-from jschauma@netmeister.org) Received: by panix.netmeister.org (Postfix, from userid 1000) id 17B948586F; Tue, 23 Nov 2021 21:08:40 -0500 (EST) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=netmeister.org; s=2021; t=1637719720; bh=CcuIFKnE2pcf0LkAV9H+lxasWwBhsrtVYM90gj5tfzE=; h=Date:From:To:Subject; b=dY1wj6q3zQCK7sWRt/0lVJxl5MmHLNBJSG3jezz59pdZVtp5fmIieAvt1MzS/SdC6 SAQgRky2tmXuk3xaVLdH12p/dcV6YDvOaPcCXPtibFTeanAM/16qUjHngCNG0tpBES zVAWLj6UpN8WxUzU/EVzSyz2Z5jTEGkV78VifGao= Date: Tue, 23 Nov 2021 21:08:39 -0500 To: freebsd-net@freebsd.org Subject: bind() to ::1 fails with EADDRNOTAVAIL / clang vs gcc Message-ID: <20211124020839.GZ11277@netmeister.org> List-Id: Networking and TCP/IP with FreeBSD List-Archive: https://lists.freebsd.org/archives/freebsd-net List-Help: List-Post: List-Subscribe: List-Unsubscribe: Sender: owner-freebsd-net@freebsd.org MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.11.1 (2018-12-01) X-Rspamd-Queue-Id: 4HzPZ80BTZz4b58 X-Spamd-Bar: --- Authentication-Results: mx1.freebsd.org; dkim=pass header.d=netmeister.org header.s=2021 header.b=dY1wj6q3; dmarc=pass (policy=quarantine) header.from=netmeister.org; spf=pass (mx1.freebsd.org: domain of jschauma@netmeister.org designates 166.84.7.99 as permitted sender) smtp.mailfrom=jschauma@netmeister.org X-Spamd-Result: default: False [-3.98 / 15.00]; ARC_NA(0.00)[]; NEURAL_HAM_MEDIUM(-0.98)[-0.977]; R_DKIM_ALLOW(-0.20)[netmeister.org:s=2021]; FROM_HAS_DN(0.00)[]; TO_MATCH_ENVRCPT_ALL(0.00)[]; R_SPF_ALLOW(-0.20)[+a]; MIME_GOOD(-0.10)[text/plain]; TO_DN_NONE(0.00)[]; NEURAL_HAM_LONG(-1.00)[-1.000]; RCPT_COUNT_ONE(0.00)[1]; DKIM_TRACE(0.00)[netmeister.org:+]; DMARC_POLICY_ALLOW(-0.50)[netmeister.org,quarantine]; NEURAL_HAM_SHORT(-1.00)[-1.000]; RCVD_COUNT_ZERO(0.00)[0]; FROM_EQ_ENVFROM(0.00)[]; MIME_TRACE(0.00)[0:+]; ASN(0.00)[asn:2033, ipnet:166.84.0.0/16, country:US]; MID_RHS_MATCH_FROM(0.00)[] Reply-To: jschauma@netmeister.org From: Jan Schaumann via freebsd-net X-Original-From: Jan Schaumann X-ThisMailContainsUnwantedMimeParts: N Hello, I'm observing the following strange behavior, where trying to bind(2) a socket on "::1" fails with EADDRNOTAVAIL, but binding in6addr_any will succeed (and then yield a bound ::1). What's more, the behavior is inconsistent depending on the compiler used. Here's my sample program a.c: ---- #include #include #include #include #include #define PORT 12345 int main(int argc, char **argv) { int sock; socklen_t a, b; struct sockaddr_storage server; struct sockaddr_in6 *sin = (struct sockaddr_in6 *)&server; if ((sock = socket(PF_INET6, SOCK_STREAM, 0)) < 0) { err(EXIT_FAILURE, "socket"); /* NOTREACHED */ } if (inet_pton(PF_INET6, "::1", &(sin->sin6_addr)) != 1) { err(EXIT_FAILURE, "inet_pton"); /* NOTREACHED */ } sin->sin6_family = PF_INET6; sin->sin6_port = htons(PORT); if (bind(sock, (struct sockaddr *)sin, sizeof(*sin)) != 0) { err(EXIT_FAILURE, "bind"); /* NOTREACHED */ } return 0; } ---- This program succeeds in binding and returns 0, as expected. However, note the declaration of the unused socklen_t a and b. If I remove that declaration, the call to bind(2) will fail: $ diff -bu [ab].c --- a.c 2021-11-23 19:49:05.926884000 +0000 +++ b.c 2021-11-23 19:48:51.409173000 +0000 @@ -11,7 +11,6 @@ int main(int argc, char **argv) { int sock; - socklen_t a, b; struct sockaddr_storage server; struct sockaddr_in6 *sin = (struct sockaddr_in6 *)&server; $ ./a.out $ echo $? 0 $ cc b.c $ ./a.out a.out: bind: Can't assign requested address $ This is on FreeBSD 13.0-RELEASE with FreeBSD clang version 11.0.1. Compiling either with gcc version 10.3.0 fails. So my questions are: - Why does _any_ of those fail? - Why does a.c succeed when compiled with clang, but b.c does not? -Jan