[ofa-general] Enabling IP_CM warns about multicast packet drops

[Or Gerlitz]

Sumeet Lahorani wrote:
> Does this packet drop always occur at the host or could it also occur in 
> the switches (Voltaire ISR 9024)?

The drop happens at the host, here's the relevant ipoib code snippet from drivers/infiniband/ulp/ipoib/ipoib_ib.c :: ipoib_send()

> 	if (unlikely(skb->len > priv->mcast_mtu + IPOIB_ENCAP_LEN)) {
> 			ipoib_warn(priv, "packet len %d (> %d) too long to send, dropping\n",
> 				   skb->len, priv->mcast_mtu + IPOIB_ENCAP_LEN);
> 			++dev->stats.tx_dropped;
> 			++dev->stats.tx_errors;
> 			ipoib_cm_skb_too_long(dev, skb, priv->mcast_mtu);
> 			return;

 
> Also, besides the "packet len too long ..." message, is the "dropped"
> statistic in ifconfig ib0 a good way to find out if such packet drops
> are happening?

yes, see the code above.

Or.