[RHEL7,COMMIT] vznetstat: Move the code to drop redundant skb marks to *_xmit() functions #PSBM-122082

Submitted by Vasily Averin on Nov. 18, 2020, 8:48 a.m.

Details

Message ID 202011180848.0AI8m5pV031659@vz7build.vvs.sw.ru
State New
Series "vznetstat: Move the code to drop redundant skb marks to *_xmit() functions #PSBM-122082"
Headers show

Commit Message

Vasily Averin Nov. 18, 2020, 8:48 a.m.
The commit is pushed to "branch-rh7-3.10.0-1127.18.2.vz7.163.x-ovz" and will appear at https://src.openvz.org/scm/ovz/vzkernel.git
after rh7-3.10.0-1127.18.2.vz7.163.44
------>
commit 02c7d2e565808125435f918a5e41f8d434c8fbf8
Author: Konstantin Khorenko <khorenko@virtuozzo.com>
Date:   Wed Nov 18 11:48:05 2020 +0300

    vznetstat: Move the code to drop redundant skb marks to *_xmit() functions #PSBM-122082
    
    We have added code to clear vz specific skb marks, but it's done in the
    hook NF_INET_LOCAL_IN (which is not the very first one) and if someone
    sets a mark with xt_mark in PREROUTING chain, the mark will be set in
    NF_INET_PRE_ROUTING hook (which is prior to NF_INET_LOCAL_IN) and
    dropped by our hook venet_acct_in_hook() in later NF_INET_LOCAL_IN hook.
    
    Example of the rule (taken from Portainer):
     -A PREROUTING -p tcp -m tcp --dport 443 -j MARK --set-xmark 0x100/0xffffffff
    
    Calltrace example where the skb mark is set by the xt_mark rule:
    
    telnet 908809 [001] probe:mark_tg: mark=0x100 skb=0xffff8b53a4ec4af8
            mark_tg+0x21 (xt_mark.ko.xz)
            ipt_do_table+0x30b ([ip_tables])
            iptable_mangle_hook+0x43 ([iptable_mangle])
     // here we have ops->hooknum == 0 == NF_INET_PRE_ROUTING
     // priority=-150 == NF_IP_PRI_MANGLE
    
            nf_iterate+0x98
            nf_hook_slow+0xa8
            ip_rcv+0x339
            __netif_receive_skb_core+0x729
            __netif_receive_skb+0x18
            process_backlog+0xae
            net_rx_action+0x27f
            __do_softirq+0x125
            call_softirq+0x1c
            do_softirq+0x65
            __local_bh_enable_ip+0x9b
            local_bh_enable+0x17
            ip_finish_output+0x284
            ip_output+0x7b
            ip_local_out_sk+0x37
            ip_queue_xmit+0x144
            tcp_transmit_skb+0x4e4
            tcp_connect+0x70d
            tcp_v4_connect+0x345
            __inet_stream_connect+0xc3
            inet_stream_connect+0x38
            SYSC_connect+0xed
            sys_connect+0xe
    
    Calltrace example where the skb mark is dropped by vznetstat hook:
    
    telnet 908809 [001] probe:venet_acct_classify_add_incoming: veid=0x142d mark=0x100 skb=0xffff8b53a4ec4af8
            venet_acct_classify_add_incoming+0x1 (vznetstat.ko.xz)
     // it's hooknum == NF_INET_LOCAL_IN == 1
     // priority      = NF_IP_PRI_FIRST
    
            nf_iterate+0x98
            nf_hook_slow+0xa8
            ip_local_deliver+0xc6
            ip_rcv_finish+0x90
            ip_rcv+0x2c0
            __netif_receive_skb_core+0x729
            __netif_receive_skb+0x18
            process_backlog+0xae
            net_rx_action+0x27f
            __do_softirq+0x125
            call_softirq+0x1c
            do_softirq+0x65
            __local_bh_enable_ip+0x9b
            local_bh_enable+0x17
            ip_finish_output+0x284
            ip_output+0x7b
            ip_local_out_sk+0x37
            ip_queue_xmit+0x144
            tcp_transmit_skb+0x4e4
            tcp_connect+0x70d
            tcp_v4_connect+0x345
            __inet_stream_connect+0xc3
            inet_stream_connect+0x38
            SYSC_connect+0xed
            sys_connect+0xe
    
    What do we do to fix this issue:
    
    1) Let's set skb marks only if the skb is going to be sent via venet or
       veth interface which are known to be a boundary between VE0 and VE.
    
       Well, in fact we need to set marks only on VE->VE0 path, but in
       venet acct "out" hook seems it's impossible to detect the direction,
       so we have to put marks on both directions.
    
       We could probably move the code for setting marks somewhere else but
       netfilter "out" hook is a convenient place for VE traffic accounting
       and as a side effect we get the correct accounting vz traffic class
       which is needed for setting correct skb mark as well,
       so let's we just here put marks on both directions.
    
    2) As "in" netfilter hook does not provide info about the skb direction
       (VE0->VE or VE->VE0), we have to move the code which drops mark from
       VE0->VE direction skbs to somewhere else.
    
       We do have knowledge of direction in *_xmit() functions,
       so let's drop redundant packet marks in venet_xmit() and veth_xmit()
       functions (as we don't currently have other network interfaces
       between VE<->VE0).
    
    3) As a side effect let's fix vz traffic accounting a bit:
       before this patch any traffic in Containers (except localhost) was
       accounted. For example the traffic between Docker Containers inside
       a single VZ Container - was accounted.
       Add a check into "in" and "out" hook to account data only in case
       "in"/"out" interfaces have NETIF_F_VENET features (i.e. are
       boundaries between VE<->VE0).
    
       Note: the VE0 accounting remains the same - there can be extra
       accounting in case of Docker Containers on host for example.
    
    ==================================
    Known issue:
    There are places (most of cases) where dst is changed in
    NF_INET_LOCAL_OUT hook, but our venet hook goes with NF_IP_PRI_LAST
    priority and no other hook uses that priority.
    So this is fine.
    
    Nevertheless there are cases when dst is changed after this case, for
    example in IPSec:
    
    iptable_nat_ipv4_out()
      nf_nat_ipv4_out()
       nf_xfrm_me_harder()
    {
    ...
             dst = xfrm_lookup(net, dst, &fl, sk, 0);
             if (IS_ERR(dst))
                     return PTR_ERR(dst);
    
             skb_dst_drop(skb);
             skb_dst_set(skb, dst);
    ...
    }
             {
                     .hook           = iptable_nat_ipv4_out,
                     .owner          = THIS_MODULE,
                     .pf             = NFPROTO_IPV4,
                     .hooknum        = NF_INET_POST_ROUTING,
                     .priority       = NF_IP_PRI_NAT_SRC,
             },
    
    And dst is changed in some exotic cases even in some *_xmit() functions.
    Well, may be for the sake of fairness we better move the vznetstat
    accounting (and setting mark) code to venet_xmit()/veth_xmit() functions
    as well, but honestly i do not make such big changes in vz7.
    
    We live with this kind of accounting for a long time and it works well
    for most usecases.
    
    So i'd leave setting mark on the same place along with accounting.
    
    Fixes: f4943221d710 ("vznetstat: Clear skb->mark on entering to VE's IP
    stack")
    https://jira.sw.ru/browse/PSBM-122082
    
    Signed-off-by: Konstantin Khorenko <khorenko@virtuozzo.com>
    
    Changes:
    v2: * extented both comments in the code and commit message
        * added similar hunks for ip6 handling
---
 drivers/net/venetdev.c              | 14 ++++++++++++++
 drivers/net/veth.c                  |  9 +++++++++
 kernel/ve/vznetstat/ip6_vznetstat.c | 20 ++++++++++++++++++++
 kernel/ve/vznetstat/ip_vznetstat.c  | 20 ++++++++++++++++++++
 kernel/ve/vznetstat/vznetstat.c     |  8 +++++---
 5 files changed, 68 insertions(+), 3 deletions(-)

Patch hide | download patch | download mbox

diff --git a/drivers/net/venetdev.c b/drivers/net/venetdev.c
index 28d06bc..3ca4f8a 100644
--- a/drivers/net/venetdev.c
+++ b/drivers/net/venetdev.c
@@ -464,6 +464,20 @@  static int venet_xmit(struct sk_buff *skb, struct net_device *dev)
 
 	stats = venet_stats(dev, smp_processor_id());
 	ve = dev_net(dev)->owner_ve;
+	/*
+	 * vzctl configures tc on Host for shaping basing on skb->marks
+	 * which are set by venet_acct_mark() basing on VE src and dst
+	 * ip address, thus vz specific marks are needed on Host only.
+	 *
+	 * On the other hand someone might set own marks inside a
+	 * Container with xt_mark funtionality, thus vz specific marks
+	 * are unexpected and undesirable inside a Container.
+	 *
+	 * => if the packet goes in VE0 -> VE direction, drop the skb
+	 * mark used for vz traffic shaping.
+	 */
+	if (ve_is_super(ve))
+		skb->mark = 0;
 
 	if (skb->protocol == __constant_htons(ETH_P_IP)) {
 		struct iphdr *iph;
diff --git a/drivers/net/veth.c b/drivers/net/veth.c
index 2fc8b91..4bbe6cc 100644
--- a/drivers/net/veth.c
+++ b/drivers/net/veth.c
@@ -149,6 +149,15 @@  static netdev_tx_t veth_xmit(struct sk_buff *skb, struct net_device *dev)
 		goto drop;
 	}
 
+	/*
+	 * If skb is going from VE0 to VE via veth,
+	 * drop the vz specific mark used for traffic shaping.
+	 * See comment in venet_xmit() for details.
+	 */
+	if (dev->features & NETIF_F_VENET &&
+	    ve_is_super(dev_net(dev)->owner_ve))
+		skb->mark = 0;
+
 	if (likely(dev_forward_skb(rcv, skb) == NET_RX_SUCCESS)) {
 		struct pcpu_vstats *stats = this_cpu_ptr(dev->vstats);
 
diff --git a/kernel/ve/vznetstat/ip6_vznetstat.c b/kernel/ve/vznetstat/ip6_vznetstat.c
index 1617de3..5eb3a8a 100644
--- a/kernel/ve/vznetstat/ip6_vznetstat.c
+++ b/kernel/ve/vznetstat/ip6_vznetstat.c
@@ -34,6 +34,17 @@  venet_acct_in_hook_v6(const struct nf_hook_ops *hook,
 
 	if (in->flags & IFF_LOOPBACK)
 		goto out;
+	/*
+	 * For VE:  let's account only traffic which crosses the coundary
+	 *	    VE0->VE.
+	 *
+	 * For VE0: let's account all the traffic as it always was.
+	 * There can be extra accounting in case of traffic between
+	 * Docker Containers in VE0.
+	 */
+	if (!ve_is_super(in->nd_net->owner_ve) &&
+	    !(in->features & NETIF_F_VENET))
+		goto out;
 
 	venet_acct_classify_add_incoming(in->nd_net->owner_ve->stat, skb);
 out:
@@ -54,6 +65,15 @@  venet_acct_out_hook_v6(const struct nf_hook_ops *hook,
 		goto out;
 	if (dst && (dst->dev->flags & IFF_LOOPBACK))
 		goto out;
+	/*
+	 * Don't account and mark VE traffic if it does not cross VE/VE0
+	 * boundary.
+	 * For VE0 there can be extra accounting in case of traffic
+	 * between Docker Containers in VE0.
+	 */
+	if (!(ve_is_super(out->nd_net->owner_ve)) &&
+	    dst && !(dst->dev->features & NETIF_F_VENET))
+		goto out;
 
 	skb->protocol = __constant_htons(ETH_P_IPV6);
 	venet_acct_classify_add_outgoing(out->nd_net->owner_ve->stat, skb);
diff --git a/kernel/ve/vznetstat/ip_vznetstat.c b/kernel/ve/vznetstat/ip_vznetstat.c
index 5ea978d..a33c41c 100644
--- a/kernel/ve/vznetstat/ip_vznetstat.c
+++ b/kernel/ve/vznetstat/ip_vznetstat.c
@@ -43,6 +43,17 @@  static unsigned int venet_acct_in_hook(const struct nf_hook_ops *hook,
 	/* Skip loopback dev */
 	if (in == dev_net(in)->loopback_dev)
 		goto out;
+	/*
+	 * For VE:  let's account only traffic which crosses the coundary
+	 *	    VE0->VE.
+	 *
+	 * For VE0: let's account all the traffic as it always was.
+	 * There can be extra accounting in case of traffic between
+	 * Docker Containers in VE0.
+	 */
+	if (!ve_is_super(in->nd_net->owner_ve) &&
+	    !(in->features & NETIF_F_VENET))
+		goto out;
 
 #if VZNS_DEBUG
 	printk("%s: in %s, out %s, size %d, in->owner_env=%s\n",
@@ -92,6 +103,15 @@  static unsigned int venet_acct_out_hook(const struct nf_hook_ops *hook,
 	 */
 	if (dst && (dst->dev->flags & IFF_LOOPBACK))
 		goto out;
+	/*
+	 * Don't account and mark VE traffic if it does not cross VE/VE0
+	 * boundary.
+	 * For VE0 there can be extra accounting in case of traffic
+	 * between Docker Containers in VE0.
+	 */
+	if (!(ve_is_super(out->nd_net->owner_ve)) &&
+	    dst && !(dst->dev->features & NETIF_F_VENET))
+		goto out;
 
 	/* Paranoia */
 	if (unlikely(!pskb_may_pull(skb, sizeof(struct iphdr))))
diff --git a/kernel/ve/vznetstat/vznetstat.c b/kernel/ve/vznetstat/vznetstat.c
index aa8d007..e03d98d 100644
--- a/kernel/ve/vznetstat/vznetstat.c
+++ b/kernel/ve/vznetstat/vznetstat.c
@@ -726,10 +726,12 @@  void venet_acct_classify_add_incoming(struct venet_stat *stat, struct sk_buff *s
 {
 	acct_one_skb(stat, skb, ACCT_IN, venet_acct_skb_size(skb));
 	/*
-	 * Every incomming skb must have zero mark, since here is its first
-	 * come into VE's IP stack.
+	 * We do set mark on skb in venet acct "out" hook so it would be
+	 * reasonable to drop redundant marks in venet acct "in" hook.
+	 * But seems it's impossible to understand the direction of
+	 * packet here (if it goes VE->VE0 or VE0->VE), thus mark is
+	 * dropped in venet_xmit() and veth_xmit() instead.
 	 */
-	venet_clear_mark(skb);
 }
 
 static inline void venet_acct_mark(struct venet_stat *stat,