netdev - Re: [net-2.6 PATCH] bonding: fix broken multicast with round-robin mode

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Date:	Wed, 31 Mar 2010 11:08:37 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Andy Gospodarek <andy@...yhouse.net>,
	David Miller <davem@...emloft.net>
Cc:	netdev@...r.kernel.org, lhh@...hat.com, fubar@...ibm.com,
	bonding-devel@...ts.sourceforge.net
Subject: Re: [net-2.6 PATCH] bonding: fix broken multicast with round-robin
 mode

Le jeudi 25 mars 2010 à 17:40 -0400, Andy Gospodarek a écrit :
> Round-robin (mode 0) does nothing to ensure that any multicast traffic
> originally destined for the host will continue to arrive at the host when
> the link that sent the IGMP join or membership report goes down.  One of
> the benefits of absolute round-robin transmit.
> 
> Keeping track of subscribed multicast groups for each slave did not seem
> like a good use of resources, so I decided to simply send on the
> curr_active slave of the bond (typically the first enslaved device that
> is up).  This makes failover management simple as IGMP membership
> reports only need to be sent when the curr_active_slave changes.  I
> tested this patch and it appears to work as expected.
> 
> Originally reported by Lon Hohberger <lhh@...hat.com>.
> 
> Signed-off-by: Andy Gospodarek <andy@...yhouse.net>
> CC: Lon Hohberger <lhh@...hat.com>
> CC: Jay Vosburgh <fubar@...ibm.com>
> 
> ---
>  drivers/net/bonding/bond_main.c |   34 ++++++++++++++++++++++++++--------
>  1 files changed, 26 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
> index 430c022..0b38455 100644
> --- a/drivers/net/bonding/bond_main.c
> +++ b/drivers/net/bonding/bond_main.c
> @@ -1235,6 +1235,11 @@ void bond_change_active_slave(struct bonding *bond, struct slave *new_active)
>  			write_lock_bh(&bond->curr_slave_lock);
>  		}
>  	}
> +
> +	/* resend IGMP joins since all were sent on curr_active_slave */
> +	if (bond->params.mode == BOND_MODE_ROUNDROBIN) {
> +		bond_resend_igmp_join_requests(bond);
> +	}
>  }
>  
>  /**
> @@ -4138,22 +4143,35 @@ static int bond_xmit_roundrobin(struct sk_buff *skb, struct net_device *bond_dev
>  	struct bonding *bond = netdev_priv(bond_dev);
>  	struct slave *slave, *start_at;
>  	int i, slave_no, res = 1;
> +	struct iphdr *iph = ip_hdr(skb);
>  
>  	read_lock(&bond->lock);
>  
>  	if (!BOND_IS_OK(bond))
>  		goto out;
> -
>  	/*
> -	 * Concurrent TX may collide on rr_tx_counter; we accept that
> -	 * as being rare enough not to justify using an atomic op here
> +	 * Start with the curr_active_slave that joined the bond as the
> +	 * default for sending IGMP traffic.  For failover purposes one
> +	 * needs to maintain some consistency for the interface that will
> +	 * send the join/membership reports.  The curr_active_slave found
> +	 * will send all of this type of traffic.
>  	 */
> -	slave_no = bond->rr_tx_counter++ % bond->slave_cnt;
> +	if ((skb->protocol == htons(ETH_P_IP)) &&
> +	    (iph->protocol == htons(IPPROTO_IGMP))) {

Hmm...

iph->protocol is a u8, how can htons(IPPROTO_IGMP) be equal to
iph->protocol ?

[PATCH] bonding: bond_xmit_roundrobin() fix

Commit a2fd940f (bonding: fix broken multicast with round-robin mode)
added a problem on litle endian machines.

drivers/net/bonding/bond_main.c:4159: warning: comparison is always
false due to limited range of data type

Signed-off-by: Eric Dumazet <eric.dumazet@...il.com>
---
diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
index 5b92fbf..5972a52 100644
--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c
@@ -4156,7 +4156,7 @@ static int bond_xmit_roundrobin(struct sk_buff *skb, struct net_device *bond_dev
 	 * send the join/membership reports.  The curr_active_slave found
 	 * will send all of this type of traffic.
 	 */
-	if ((iph->protocol == htons(IPPROTO_IGMP)) &&
+	if ((iph->protocol == IPPROTO_IGMP) &&
 	    (skb->protocol == htons(ETH_P_IP))) {
 
 		read_lock(&bond->curr_slave_lock);



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