netdev - Re: [PATCH RFC 3/3] RDMA/siw: Require non-zero 6-byte MACs for soft iWARP

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Date: Wed, 31 May 2023 19:11:52 +0000
From: Chuck Lever III <chuck.lever@...cle.com>
To: Jason Gunthorpe <jgg@...pe.ca>
CC: Chuck Lever <cel@...nel.org>, Netdev <netdev@...r.kernel.org>,
        linux-rdma
	<linux-rdma@...r.kernel.org>,
        Bernard Metzler <BMT@...ich.ibm.com>, Tom
 Talpey <tom@...pey.com>
Subject: Re: [PATCH RFC 3/3] RDMA/siw: Require non-zero 6-byte MACs for soft
 iWARP



> On May 31, 2023, at 3:04 PM, Jason Gunthorpe <jgg@...pe.ca> wrote:
> 
> On Tue, May 23, 2023 at 07:18:18PM +0000, Chuck Lever III wrote:
> 
>> The core address resolution code wants to find an L2 address
>> for the egress device. The underlying ib_device, where a made-up
>> GID might be stored, is not involved with address resolution
>> AFAICT.
> 
> Where are you hitting this?

     kworker/2:0-26    [002]   551.962874: funcgraph_entry:                   |  addr_resolve() {
     kworker/2:0-26    [002]   551.962874: bprint:               addr_resolve: resolve_neigh=true resolve_by_gid_attr=false
     kworker/2:0-26    [002]   551.962874: funcgraph_entry:                   |    addr4_resolve.constprop.0() {
     kworker/2:0-26    [002]   551.962875: bprint:               addr4_resolve.constprop.0: src_in=0.0.0.0:35173 dst_in=100.72.1.2:20049
     kworker/2:0-26    [002]   551.962875: funcgraph_entry:                   |      ip_route_output_flow() {
     kworker/2:0-26    [002]   551.962875: funcgraph_entry:                   |        ip_route_output_key_hash() {
     kworker/2:0-26    [002]   551.962876: funcgraph_entry:                   |          ip_route_output_key_hash_rcu() {
     kworker/2:0-26    [002]   551.962876: funcgraph_entry:        4.526 us   |            __fib_lookup();
     kworker/2:0-26    [002]   551.962881: funcgraph_entry:        0.264 us   |            fib_select_path();
     kworker/2:0-26    [002]   551.962881: funcgraph_entry:        1.022 us   |            __mkroute_output();
     kworker/2:0-26    [002]   551.962882: funcgraph_exit:         6.705 us   |          }
     kworker/2:0-26    [002]   551.962882: funcgraph_exit:         7.283 us   |        }
     kworker/2:0-26    [002]   551.962883: funcgraph_exit:         7.624 us   |      }
     kworker/2:0-26    [002]   551.962883: funcgraph_exit:         8.395 us   |    }
     kworker/2:0-26    [002]   551.962883: funcgraph_entry:                   |    rdma_set_src_addr_rcu.constprop.0() {
     kworker/2:0-26    [002]   551.962883: bprint:               rdma_set_src_addr_rcu.constprop.0: ndev=0xffff91f5135a4000 name=tailscale0
     kworker/2:0-26    [002]   551.962884: funcgraph_entry:                   |      copy_src_l2_addr() {
     kworker/2:0-26    [002]   551.962884: funcgraph_entry:        0.984 us   |        iff_flags2string();
     kworker/2:0-26    [002]   551.962885: bprint:               copy_src_l2_addr: ndev=0xffff91f5135a4000 dst_in=100.72.1.2:20049 flags=UP|POINTOPOINT|NOARP|MULTICAST
     kworker/2:0-26    [002]   551.962885: funcgraph_entry:                   |        rdma_copy_src_l2_addr() {
     kworker/2:0-26    [002]   551.962886: funcgraph_entry:        0.148 us   |          devtype2string();
     kworker/2:0-26    [002]   551.962887: bprint:               rdma_copy_src_l2_addr: name=tailscale0 type=NONE src_dev_addr=00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 broadcast=00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ifindex=3
     kworker/2:0-26    [002]   551.962887: funcgraph_exit:         1.488 us   |        }
     kworker/2:0-26    [002]   551.962887: bprint:               copy_src_l2_addr: network type=IB
     kworker/2:0-26    [002]   551.962887: funcgraph_exit:         3.636 us   |      }
     kworker/2:0-26    [002]   551.962887: funcgraph_exit:         4.275 us   |    }


Address resolution finds the right device, but there's
a zero-value L2 address. Thus it cannot form a unique
GID from that. Perhaps there needs to be a call to
query_gid in here?


--
Chuck Lever