From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by passt.top (Postfix) with ESMTP id 356535A0272 for ; Wed, 20 Mar 2024 11:52:05 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1710931924; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=WS6hsmUkbZfhfweF+AU83p4xObVcMLjRRitaeBfqLwc=; b=N+azphjLlaN1fTR/ySd739s9iY4SADLyo0kSlV68oxatoBuud4q6t4fPle+nX3S0WXi/ky HTxU1rzVkU1Bwfnxu12T0quPerp9rR4Hy8o2xOuYSvU5c7ydcOawQ7lPV1xx2ki5zqhVlH Qaj9vx/8CJXeYWBLTsuLc4CZAZ3Huz8= Received: from mail-wm1-f71.google.com (mail-wm1-f71.google.com [209.85.128.71]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-324-M7DxgpqpO6qLHvgMes0wZg-1; Wed, 20 Mar 2024 06:52:02 -0400 X-MC-Unique: M7DxgpqpO6qLHvgMes0wZg-1 Received: by mail-wm1-f71.google.com with SMTP id 5b1f17b1804b1-4140a509ee9so18615885e9.3 for ; Wed, 20 Mar 2024 03:52:02 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1710931921; x=1711536721; h=content-transfer-encoding:in-reply-to:from:references:to :content-language:subject:user-agent:mime-version:date:message-id :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=WS6hsmUkbZfhfweF+AU83p4xObVcMLjRRitaeBfqLwc=; b=EF6D47wFxUDezTl8zEqJy1DXrr4NcC+ID+5xLZ8irkLyXIJ78KHjqUD2qTkCpIlTwY rFOtvawEAQUUCZBzZxMj0ARtPHf0+aWnt+Xa+cuEmsJfRxM0cDNbRNvXgb6mwkdlXvYj 9biNMcAZodntS3aPnTL4IWTaEFS6Aw9Kqdv9zbvXLup5488WW4VBwlNRD+R6bbhRAVlQ 6BnViCtb7buIPhJVDMlHrrWzRsDF2zA/FFHdL2Zzvzh3DlD61oxTW0kNjmV1hSAJH4f7 FMZ1M1rwxNiYxu+hbmv9eEDKXafxbXENcQPdy1UsMRH6JIdVi9xmjp02iXp6A/fNtCua 1Orw== X-Forwarded-Encrypted: i=1; AJvYcCVElSSWAJU+FYcbU0UuW0hl1cvjXaD97UPz887XPmXNd7B9bPk0YQFThskIwMYBJnXLllejLwPjy3ulcJkVWTNBu5JD X-Gm-Message-State: AOJu0Yy8t7CK3vILtfdVphvb6TbvKzKVLlQsboQMsjenlLfw2OO0wk5I cXgTJmeKULnKCiNJ9MkK2IKA04ZWebJnjM9BMxIOI/uhsmEuKungSHkrKJ7pNgJKVn2xGzs4PCY 1gwfZ+br0fh1p/9emLbu+HjXDU5VtLUF+l6w/IKii/zIj++Eezw== X-Received: by 2002:a05:600c:46cf:b0:414:a54:ec04 with SMTP id q15-20020a05600c46cf00b004140a54ec04mr1351699wmo.4.1710931921081; Wed, 20 Mar 2024 03:52:01 -0700 (PDT) X-Google-Smtp-Source: AGHT+IH7jW8w1wrq4pHgVsmdZ+bSEgTo2+xhbfvWPPbDJxlpVLTscrQ+hD6TXNREwsNsaRGb1lHqqA== X-Received: by 2002:a05:600c:46cf:b0:414:a54:ec04 with SMTP id q15-20020a05600c46cf00b004140a54ec04mr1351689wmo.4.1710931920723; Wed, 20 Mar 2024 03:52:00 -0700 (PDT) Received: from [192.168.188.25] ([80.243.52.135]) by smtp.gmail.com with ESMTPSA id m14-20020a05600c4f4e00b00413f4cb62e1sm1856264wmq.23.2024.03.20.03.52.00 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 20 Mar 2024 03:52:00 -0700 (PDT) Message-ID: <80107179-5357-4b14-94ae-c82925a97ba8@redhat.com> Date: Wed, 20 Mar 2024 11:51:59 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] netlink: Fix selection of template interface To: David Gibson , passt-dev@passt.top, Stefano Brivio References: <20240320053339.553418-1-david@gibson.dropbear.id.au> From: Paul Holzinger In-Reply-To: <20240320053339.553418-1-david@gibson.dropbear.id.au> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Message-ID-Hash: GRKVXXRNVY2KHFNBK2MQKGO54R334XBN X-Message-ID-Hash: GRKVXXRNVY2KHFNBK2MQKGO54R334XBN X-MailFrom: pholzing@redhat.com X-Mailman-Rule-Misses: dmarc-mitigation; no-senders; approved; emergency; loop; banned-address; member-moderation; nonmember-moderation; administrivia; implicit-dest; max-recipients; max-size; news-moderation; no-subject; digests; suspicious-header X-Mailman-Version: 3.3.8 Precedence: list List-Id: Development discussion and patches for passt Archived-At: Archived-At: List-Archive: List-Archive: List-Help: List-Owner: List-Post: List-Subscribe: List-Unsubscribe: On 20/03/2024 06:33, David Gibson wrote: > Since f919dc7a4b1c ("conf, netlink: Don't require a default route to > start"), if there is only one host interface with routes, we will pick that > as the template interface, even if there are no default routes for an IP > version. Unfortunately this selection had a serious flaw: in some cases > it would 'return' in the middle of an nl_foreach() loop, meaning we > wouldn't consume all the netlink responses for our query. This could cause > later netlink operations to fail as we read leftover responses from the > aborted query. > > Rewrite the interface detection to avoid this problem. While we're there: > * Perform detection of both default and non-default routes in a single > pass, avoiding an ugly goto > * Give more detail on error and working but unusual paths about the > situation (no suitable interface, multiple possible candidates, etc.). > > Fixes: f919dc7a4b1c ("conf, netlink: Don't require a default route to start") > Link: https://bugs.passt.top/show_bug.cgi?id=83 > Link: https://github.com/containers/podman/issues/22052 > Link: https://bugzilla.redhat.com/show_bug.cgi?id=2270257 > > Signed-off-by: David Gibson > --- > conf.c | 4 ++-- > netlink.c | 62 ++++++++++++++++++++++++++++++++++--------------------- > 2 files changed, 40 insertions(+), 26 deletions(-) > > diff --git a/conf.c b/conf.c > index 644752cc..9e0318a5 100644 > --- a/conf.c > +++ b/conf.c > @@ -584,7 +584,7 @@ static unsigned int conf_ip4(unsigned int ifi, > ifi = nl_get_ext_if(nl_sock, AF_INET); > > if (!ifi) { > - info("No interface with a route for IPv4: disabling IPv4"); > + info("Couldn't pick external interface: disabling IPv4"); > return 0; > } > > @@ -656,7 +656,7 @@ static unsigned int conf_ip6(unsigned int ifi, > ifi = nl_get_ext_if(nl_sock, AF_INET6); > > if (!ifi) { > - info("No interface with a route for IPv6: disabling IPv6"); > + info("Couldn't pick external interface: disabling IPv6"); > return 0; > } > > diff --git a/netlink.c b/netlink.c > index 632304c1..c0a5f158 100644 > --- a/netlink.c > +++ b/netlink.c > @@ -254,8 +254,8 @@ unsigned int nl_get_ext_if(int s, sa_family_t af) > .rtm.rtm_type = RTN_UNICAST, > .rtm.rtm_family = af, > }; > - bool default_only = true; > - unsigned int ifi = 0; > + unsigned defifi = 0, anyifi = 0; > + unsigned ndef = 0, nany = 0; > struct nlmsghdr *nh; > struct rtattr *rta; > char buf[NLBUFSIZ]; > @@ -263,7 +263,6 @@ unsigned int nl_get_ext_if(int s, sa_family_t af) > uint32_t seq; > size_t na; > > -again: > /* Look for an interface with a default route first, failing that, look > * for any interface with a route, and pick it only if it's the only > * interface with a route. > @@ -271,46 +270,61 @@ again: > seq = nl_send(s, &req, RTM_GETROUTE, NLM_F_DUMP, sizeof(req)); > nl_foreach_oftype(nh, status, s, buf, seq, RTM_NEWROUTE) { > struct rtmsg *rtm = (struct rtmsg *)NLMSG_DATA(nh); > + unsigned thisifi = 0; > > - if (default_only) { > - if (ifi || rtm->rtm_dst_len || rtm->rtm_family != af) > - continue; > - } else { > - if (rtm->rtm_family != af) > - continue; > - } > + if (rtm->rtm_family != af) > + continue; > > for (rta = RTM_RTA(rtm), na = RTM_PAYLOAD(nh); RTA_OK(rta, na); > rta = RTA_NEXT(rta, na)) { > if (rta->rta_type == RTA_OIF) { > - if (!default_only && ifi && > - ifi != *(unsigned int *)RTA_DATA(rta)) > - return 0; > - > - ifi = *(unsigned int *)RTA_DATA(rta); > + thisifi = *(unsigned int *)RTA_DATA(rta); > } else if (rta->rta_type == RTA_MULTIPATH) { > const struct rtnexthop *rtnh; > > rtnh = (struct rtnexthop *)RTA_DATA(rta); > + thisifi = rtnh->rtnh_ifindex; > + } > + } > > - if (!default_only && ifi && > - (int)ifi != rtnh->rtnh_ifindex) > - return 0; > + if (!thisifi) > + continue; /* No interface for this route */ > > - ifi = rtnh->rtnh_ifindex; > - } > + if (rtm->rtm_dst_len == 0) { > + /* Default route */ > + ndef++; > + if (!defifi) > + defifi = thisifi; > + } else { > + /* Non-default route */ > + nany++; > + if (!anyifi) > + anyifi = thisifi; > } > } > > if (status < 0) > warn("netlink: RTM_GETROUTE failed: %s", strerror(-status)); > > - if (!ifi && default_only) { > - default_only = false; > - goto again; > + if (defifi) { > + if (ndef > 1) > + info("Multiple default %s routes, picked first", > + af == AF_INET ? "IPv4" : "IPv6"); > + return defifi; > } > > - return ifi; > + if (anyifi) { > + if (nany == 1) > + return anyifi; > + > + warn("Multiple interfaces with %s routes, use -i to select one", > + af == AF_INET ? "IPv4" : "IPv6"); This should not be a warning, for me this always triggers because I have two interfaces with link local addresses and no global ipv6 route as I do not have any ipv6 connection. Or maybe the correct fix is to never consider ipv6 link local routes for this logic? At least I cannot see the purpose of using a interface with only a link local route. > + } > + > + if (!nany) > + warn("No interfaces with %s routes", af == AF_INET ? "IPv4" : "IPv6"); > + > + return 0; > } > > /** I reproduced by having a second interface and confirm this patch fixes it.