Re: [PATCH v4 1/1] ibacm: Add support for pathrecord query through netlink

[Hal Rosenstock <hal-LDSdmyG8hGV8YrgS2mwiifqBs+8SCbDb@public.gmane.org>]

On 6/11/2015 10:25 AM, Wan, Kaike wrote:

>>> +static void acm_nl_process_resolve(struct acmc_client *client,
>>> +				   struct acm_nl_msg *acmnlmsg)
>>> +{
>>> +	struct acm_msg msg;
>>> +	struct nlattr *attr;
>>> +	int payload_len;
>>> +	int rem;
>>> +	int total_attr_len;
>>> +
>>> +	memset(&msg, 0, sizeof(msg));
>>> +	msg.hdr.opcode = ACM_OP_RESOLVE;
>>> +	msg.hdr.version = ACM_VERSION;
>>> +	msg.hdr.length = ACM_MSG_HDR_LENGTH +
>> ACM_MSG_EP_LENGTH;
>>> +	msg.hdr.status = ACM_STATUS_SUCCESS;
>>> +	msg.hdr.tid = (uint64_t) acmnlmsg;
>>> +	msg.resolve_data[0].type = ACM_EP_INFO_PATH;
>>> +
>>> +	payload_len = acmnlmsg->nlmsg_header.nlmsg_len -
>> NLMSG_HDRLEN;
>>> +	attr = NLMSG_DATA(&acmnlmsg->nlmsg_header);
>>> +	rem = payload_len;
>>> +	while (1) {
>>> +		if (rem < (int) sizeof(*attr) ||
>>> +		    attr->nla_len < sizeof(*attr) ||
>>> +		    attr->nla_len > rem)
>>> +			break;
>>> +
>>> +		acm_nl_parse_path_attr(attr, &msg.resolve_data[0]);
>>> +
>>> +		/* Next attribute */
>>> +		total_attr_len = NLA_ALIGN(attr->nla_len);
>>> +		rem -= total_attr_len;
>>> +		attr = (struct nlattr *) ((char *) attr + total_attr_len);
>>> +	}
>>> +
>>
>> Since ACM does not resolve multicast PRs,
> 
> Why not? The multicast gid will be used as the dgid and ibacm will not ask peers for address resolution. 
> Instead, It will ask SA directly for the multicast pathrecord (route resolution only). 
> I can't see why it can't be done here.

Are you saying the local cache lookup fails so it falls back to ask SA
for multicast PR ? If so, then perhaps there's provider optimization to
fail that style of lookup rather than doing the tree lookup.

>> as an optimization here, some
>> minor check of DGID could be done and if it's multicast DGID, ENODATA
>> could be indicated in NL message.
>>
> 

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