From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 3F33E12BF13 for ; Tue, 6 Feb 2024 08:43:24 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1707209006; cv=none; b=EefWmNtG4CDpkG87FJJvqy4VY2EMPE9LXzB2qV419TRgbLahn1Ve1QeDYS6UR2BbAlkUBq/AIsWojzBI8MfpkgirE7Sdt96S5bPBiTAcEXYTwn8R7HbBZEcXRuF6H9tzcjUfb3C0ZLEZeGXzryHS4AQ70gje6AVxI+2DdFbf0Co= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1707209006; c=relaxed/simple; bh=4kUF1dsqZ3HydIu0UmZlVkoFVYPz8YhNJl31ieHIyoY=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=QVgdGnfE4YBpU1e1NoYdbQldKv+s/yMtXBbRziqtLTG9Rs6OvVYhSifKKF/9hQLDotuH/slb3PzVxYIatuDYrFq8lB2U6ddzpjDewUl7KE+hZqaUAWRgou8K3G4/RcdOG4LnN/MzAHV5raPEx1iaKnaMgah9HrbbUMBFN/Ncn4Q= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=DgQs0CXd; arc=none smtp.client-ip=170.10.129.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="DgQs0CXd" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1707209004; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:autocrypt:autocrypt; bh=TLq3ye7gMCI0pAC3vStirIbgKgIsTAMc8Eh5rpxxxgc=; b=DgQs0CXdD8Hv+9REv83zhmwXwzi3wa+XfDJaGtgcJ0A4lvi+fbpB00j/sxlBXQxjIEVcym 0SErBHWPoAFFi6nRMaPCZHu7O/hxgbtse4rmW4p4VhBuD5ovzogWykI+w9T8j17dQC9eKx 5GorTABND6Vc4H6T09Dj6NK4CMOQrXQ= Received: from mail-lf1-f71.google.com (mail-lf1-f71.google.com [209.85.167.71]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-221-Y9l4vPqoO7q77xPbvYlfqQ-1; Tue, 06 Feb 2024 03:43:22 -0500 X-MC-Unique: Y9l4vPqoO7q77xPbvYlfqQ-1 Received: by mail-lf1-f71.google.com with SMTP id 2adb3069b0e04-50e93545a26so1534512e87.0 for ; Tue, 06 Feb 2024 00:43:22 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1707209000; x=1707813800; h=mime-version:user-agent:content-transfer-encoding:autocrypt :references:in-reply-to:date:cc:to:from:subject:message-id :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=TLq3ye7gMCI0pAC3vStirIbgKgIsTAMc8Eh5rpxxxgc=; b=ctznde/O1z3U5BnDE+SUbLcQu353AgKnlZ9BTvIxgOQPmsEdoPU0RhWrifJEVrOF6f pr9UwrqKv464L/J9LSda4U5coe6Tbm/v9Mdru7mZbie5DXFjDmW8Tgs7HuV/HXpff6F5 32wTHJBIUzbkyMWG+TMm/Qggu+qxNXu5doWOQ2VChOCOGYR2G0ZtA3f9kv3VEo/upE00 7201ZHiYtMOqYltFlivUuVQChc6hVEjLsFbUAL8LOKiICd+t0gmCx3fyQTfjadix7IjG /zQMm71RED+xPUmu+r4ThpW0ovcbPaKiVzAMPHCicOE2KGVom32ZHwiW4/o3x6E89jA4 93lg== X-Gm-Message-State: AOJu0YxcO89zkvqpqn4gsdKQXo3oNTpq6Pm3/nQhuAVafaUIccxbd64/ ZZfyciKXgtBlhwoBa+GidhxF1X28gSYSsUl7HzutR+PPo8KgusuiKTc82QV+2lr1Te4IksRh11U KyMR6q9uxVHH74DpzfT0TJ4+bh2adQYPCT6ZQVrsOWkV5rxKU6FgwJZOx9ieeuqa+HA== X-Received: by 2002:a19:e01c:0:b0:511:4881:1b6d with SMTP id x28-20020a19e01c000000b0051148811b6dmr1133568lfg.1.1707209000470; Tue, 06 Feb 2024 00:43:20 -0800 (PST) X-Google-Smtp-Source: AGHT+IGjuD+flFVmy5XKfDIjacx28CSlDoqwFqJ4jwV3YQ+8SK8l48LEpLPowDDXO7YJrPXNewNyHA== X-Received: by 2002:a19:e01c:0:b0:511:4881:1b6d with SMTP id x28-20020a19e01c000000b0051148811b6dmr1133553lfg.1.1707209000075; Tue, 06 Feb 2024 00:43:20 -0800 (PST) X-Forwarded-Encrypted: i=0; AJvYcCXD1eN72LWEimGgaifuJWs5pa1umg2e4HMNCu73A5+Iq1LJr8JGeIQrYCHMsg8uGF8pww+OKWqWpk2UJa++zh+F5Zcc2FGq Received: from gerbillo.redhat.com (146-241-224-127.dyn.eolo.it. [146.241.224.127]) by smtp.gmail.com with ESMTPSA id dn17-20020a05600c655100b0040fc2b3d852sm1198646wmb.30.2024.02.06.00.43.19 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 06 Feb 2024 00:43:19 -0800 (PST) Message-ID: <852606cd9cbc8da9c6735b4ad6216ba55408b767.camel@redhat.com> Subject: Re: The sk_err mechanism is infuriating in userspace From: Paolo Abeni To: Andy Lutomirski , Network Development Cc: Linux API Date: Tue, 06 Feb 2024 09:43:18 +0100 In-Reply-To: References: Autocrypt: addr=pabeni@redhat.com; prefer-encrypt=mutual; keydata=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 7ZxN9ZsDL38qVIuFkSpgMZCiUHdxBC11J8nbBSLlpnc924UAyr5XrGA99 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 iWjoCy8L35zPqR5TV+f5WR5hTVCqmLHSgm1jxwKhPg9L+GfuE4d0SWd84y 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 sD2W1U7eyLdm/jCgticGDsRtweytsgCSYfbz0gdgUuL3EBYN3JLbAU+UZpy 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 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.50.3 (3.50.3-1.fc39) Precedence: bulk X-Mailing-List: linux-api@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Mon, 2024-02-05 at 15:03 -0800, Andy Lutomirski wrote: > Hi all- >=20 > I encounter this issue every couple of years, and it still seems to be > an issue, and it drives me nuts every time I see it. >=20 > I write software that uses unconnected datagram-style sockets. Errors > happen for all kinds of reasons, and my software knows it. My > software even handles the errors and moves on with its life. I use > MSG_ERRQUEUE to understand the errors. But the kernel fights back: >=20 > struct sk_buff *__skb_try_recv_datagram(struct sock *sk, > struct sk_buff_head *queue, > unsigned int flags, int *off, int= *err, > struct sk_buff **last) > { > struct sk_buff *skb; > unsigned long cpu_flags; > /* > * Caller is allowed not to check sk->sk_err before skb_recv_data= gram() > */ > int error =3D sock_error(sk); >=20 > if (error) > goto no_packet; > ^^^^^^^^^^ <----- EXCUSE ME? >=20 > The kernel even fights back on the *send* path?!? >=20 > static long sock_wait_for_wmem(struct sock *sk, long timeo) > { > DEFINE_WAIT(wait); >=20 > sk_clear_bit(SOCKWQ_ASYNC_NOSPACE, sk); > for (;;) { > if (!timeo) > break; > if (signal_pending(current)) > break; > set_bit(SOCK_NOSPACE, &sk->sk_socket->flags); > ... > if (READ_ONCE(sk->sk_err)) > break; <-- KERNEL HATES UNCONNECTED SOCKETS! >=20 > This is IMO just broken. I realize it's legacy behavior, but it's > BROKEN legacy behavior.=C2=A0 As you noted this is an established behaviour exposed to the user- space, and we can't simply change it, regardless of it's own (eventual lack of) merit. > sk_err does not (at least for an unconnected > socket) indicate that anything is wrong with the socket.=20 What about 'destination/port unreachable' and many other similar errors reported by sk_err? Which specific errors reported by sk_err does not indicate that anything is wrong with the socket ? I guess that if you really want to ignore socket error for datagram sockets at recvmsg()/sendmsg() time you could implement some new socket option to conditionally enable such behaviour on a per socket basis. Cheers, Paolo