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SubjectRe: question about bonding mode 4
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Any comments? Thanks!

On 2021/1/15 10:02, moyufeng wrote:
> Hi Team,
>
> I have a question about bonding. During testing bonding mode 4
> scenarios, I find that there is a very low probability that
> the pointer is null. The following information is displayed:
>
> [99359.795934] bond0: (slave eth13.2001): Port 2 did not find a suitable aggregator
> [99359.796960] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000020
> [99359.798127] Mem abort info:
> [99359.798526] ESR = 0x96000004
> [99359.798938] EC = 0x25: DABT (current EL), IL = 32 bits
> [99359.799673] SET = 0, FnV = 0
> [99359.800106] EA = 0, S1PTW = 0
> [99359.800554] Data abort info:
> [99359.800952] ISV = 0, ISS = 0x00000004
> [99359.801522] CM = 0, WnR = 0
> [99359.801970] user pgtable: 4k pages, 48-bit VAs, pgdp=00000000c64e6000
> [99359.802876] [0000000000000020] pgd=0000000000000000
> [99359.803555] Internal error: Oops: 96000004 [#1] PREEMPT SMP
> [99359.804369] Modules linked in: bonding hns3(-) hclgevf hnae3 [last unloaded: bonding]
> [99359.805494] CPU: 1 PID: 951 Comm: kworker/u10:2 Not tainted 5.7.0-rc4+ #1
> [99359.806455] Hardware name: linux,dummy-virt (DT)
> [99359.807107] Workqueue: bond0 bond_3ad_state_machine_handler [bonding]
> [99359.808056] pstate: 60c00005 (nZCv daif +PAN +UAO)
> [99359.808722] pc : bond_3ad_state_machine_handler+0x7fc/0xdb8 [bonding]
> [99359.809652] lr : bond_3ad_state_machine_handler+0x7f4/0xdb8 [bonding]
> [99359.810535] sp : ffff80001882bd20
> [99359.811012] x29: ffff80001882bd20 x28: ffff000085939a38
> [99359.811791] x27: ffff00008649bb68 x26: 00000000aaaaaaab
> [99359.812871] x25: ffff800009401000 x24: ffff800009408de4
> [99359.814049] x23: ffff80001882bd98 x22: ffff00008649b880
> [99359.815210] x21: 0000000000000000 x20: ffff000085939a00
> [99359.816401] x19: ffff00008649b880 x18: ffff800012572988
> [99359.817637] x17: 0000000000000000 x16: 0000000000000000
> [99359.818870] x15: ffff80009882b987 x14: 726f746167657267
> [99359.820090] x13: 676120656c626174 x12: 697573206120646e
> [99359.821374] x11: 696620746f6e2064 x10: 696420322074726f
> [99359.822659] x9 : 50203a2931303032 x8 : 0000000000081391
> [99359.823891] x7 : ffff8000108e3ad0 x6 : ffff8000128858bb
> [99359.825109] x5 : 0000000000000000 x4 : 0000000000000000
> [99359.826262] x3 : 00000000ffffffff x2 : 906b329bb5362a00
> [99359.827394] x1 : 906b329bb5362a00 x0 : 0000000000000000
> [99359.828540] Call trace:
> [99359.829071] bond_3ad_state_machine_handler+0x7fc/0xdb8 [bonding]
> [99359.830367] process_one_work+0x15c/0x4a0
> [99359.831216] worker_thread+0x50/0x478
> [99359.832022] kthread+0x130/0x160
> [99359.832716] ret_from_fork+0x10/0x18
> [99359.833487] Code: 910c0021 95f704bb f9403f80 b5ffe300 (f9401000)
> [99359.834742] ---[ end trace c7a8e02914afc4e0 ]---
> [99359.835817] Kernel panic - not syncing: Fatal exception in interrupt
> [99359.837334] SMP: stopping secondary CPUs
> [99359.838277] Kernel Offset: disabled
> [99359.839086] CPU features: 0x080002,22208218
> [99359.840053] Memory Limit: none
> [99359.840783] ---[ end Kernel panic - not syncing: Fatal exception in interrupt ]---
>
> The test procedure is as follows:
> 1. Configure bonding and set it to mode 4.
> echo "4" > /sys/class/net/bond0/bonding/mode
> ifconfig bond0 up
>
> 2. Configure two VLANs and add them to the bonding in step 1.
> vconfig add eth0 2001
> vconfig add eth1 2001
> ifenslave bond0 eth0.2001 eth1.2001
>
> 3. Unload the network device driver and bonding driver.
> rmmod hns3
> rmmod hclge
> rmmod hnae3
> rmmod bonding.ko
>
> 4. Repeat the preceding steps for a long time.
>
> By checking the logic in ad_port_selection_logic(), I find that
> if enter the branch "Port %d did not find a suitable aggregator",
> the value of port->aggregator will be NULL, causing the problem.
>
> So I'd like to ask what circumstances will be involved in this
> branch, and what should be done in this case?
>
>
> The detailed code analysis is as follows:
>
> static void ad_port_selection_logic(struct port *port, bool *update_slave_arr)
> {
> [...]
> /* if the port is connected to other aggregator, detach it */
> if (port->aggregator) {
> /* detach the port from its former aggregator */
> temp_aggregator = port->aggregator;
> for (curr_port = temp_aggregator->lag_ports; curr_port;
> last_port = curr_port,
> curr_port = curr_port->next_port_in_aggregator) {
> if (curr_port == port) {
> temp_aggregator->num_of_ports--;
> /* if it is the first port attached to the
> * aggregator
> */
> if (!last_port) {
> temp_aggregator->lag_ports =
> port->next_port_in_aggregator;
> } else {
> /* not the first port attached to the
> * aggregator
> */
> last_port->next_port_in_aggregator =
> port->next_port_in_aggregator;
> }
>
> /* clear the port's relations to this
> * aggregator
> */
> port->aggregator = NULL;
>
> ----analysis: set port->aggregator NULL at the beginning of ad_port_selection_logic().
>
> port->next_port_in_aggregator = NULL;
> port->actor_port_aggregator_identifier = 0;
>
> slave_dbg(bond->dev, port->slave->dev, "Port %d left LAG %d\n",
> port->actor_port_number,
> temp_aggregator->aggregator_identifier);
> /* if the aggregator is empty, clear its
> * parameters, and set it ready to be attached
> */
> if (!temp_aggregator->lag_ports)
> ad_clear_agg(temp_aggregator);
> break;
> }
> }
> if (!curr_port) {
> /* meaning: the port was related to an aggregator
> * but was not on the aggregator port list
> */
> net_warn_ratelimited("%s: (slave %s): Warning: Port %d was related to aggregator %d but was not on its port list\n",
> port->slave->bond->dev->name,
> port->slave->dev->name,
> port->actor_port_number,
> port->aggregator->aggregator_identifier);
> }
> }
> /* search on all aggregators for a suitable aggregator for this port */
> bond_for_each_slave(bond, slave, iter) {
> aggregator = &(SLAVE_AD_INFO(slave)->aggregator);
> /* keep a free aggregator for later use(if needed) */
> if (!aggregator->lag_ports) {
> if (!free_aggregator)
> free_aggregator = aggregator;
>
> ----analysis: Save free_aggregator if found a free aggregator. But in this case, no free aggregator is available.
>
> continue;
> }
> /* check if current aggregator suits us */
> if (((aggregator->actor_oper_aggregator_key == port->actor_oper_port_key) && /* if all parameters match AND */
> MAC_ADDRESS_EQUAL(&(aggregator->partner_system), &(port->partner_oper.system)) &&
> (aggregator->partner_system_priority == port->partner_oper.system_priority) &&
> (aggregator->partner_oper_aggregator_key == port->partner_oper.key)
> ) &&
> ((!MAC_ADDRESS_EQUAL(&(port->partner_oper.system), &(null_mac_addr)) && /* partner answers */
> !aggregator->is_individual) /* but is not individual OR */
> )
> ) {
> /* attach to the founded aggregator */
> port->aggregator = aggregator;
>
> ----analysis: If a proper aggregator is found, port->aggregator is assigned here.
>
> port->actor_port_aggregator_identifier =
> port->aggregator->aggregator_identifier;
> port->next_port_in_aggregator = aggregator->lag_ports;
> port->aggregator->num_of_ports++;
> aggregator->lag_ports = port;
> slave_dbg(bond->dev, slave->dev, "Port %d joined LAG %d (existing LAG)\n",
> port->actor_port_number,
> port->aggregator->aggregator_identifier);
>
> /* mark this port as selected */
> port->sm_vars |= AD_PORT_SELECTED;
> found = 1;
>
> ----analysis: Set found to 1 if port->aggregator is assigned.
>
> break;
> }
> }
> /* the port couldn't find an aggregator - attach it to a new
> * aggregator
> */
> if (!found) {
> if (free_aggregator) {
> /* assign port a new aggregator */
> port->aggregator = free_aggregator;
>
> ----analysis: No proper free_aggregator is found. Therefore, port->aggregator cannot be assigned here.
>
> port->actor_port_aggregator_identifier =
> port->aggregator->aggregator_identifier;
>
> /* update the new aggregator's parameters
> * if port was responsed from the end-user
> */
> if (port->actor_oper_port_key & AD_DUPLEX_KEY_MASKS)
> /* if port is full duplex */
> port->aggregator->is_individual = false;
> else
> port->aggregator->is_individual = true;
>
> port->aggregator->actor_admin_aggregator_key =
> port->actor_admin_port_key;
> port->aggregator->actor_oper_aggregator_key =
> port->actor_oper_port_key;
> port->aggregator->partner_system =
> port->partner_oper.system;
> port->aggregator->partner_system_priority =
> port->partner_oper.system_priority;
> port->aggregator->partner_oper_aggregator_key = port->partner_oper.key;
> port->aggregator->receive_state = 1;
> port->aggregator->transmit_state = 1;
> port->aggregator->lag_ports = port;
> port->aggregator->num_of_ports++;
>
> /* mark this port as selected */
> port->sm_vars |= AD_PORT_SELECTED;
>
> slave_dbg(bond->dev, port->slave->dev, "Port %d joined LAG %d (new LAG)\n",
> port->actor_port_number,
> port->aggregator->aggregator_identifier);
> } else {
> slave_err(bond->dev, port->slave->dev,
> "Port %d did not find a suitable aggregator\n",
> port->actor_port_number);
>
> ----analysis: The fault scenario goes to this branch, and port->aggregator remains NULL.
>
> }
> }
> /* if all aggregator's ports are READY_N == TRUE, set ready=TRUE
> * in all aggregator's ports, else set ready=FALSE in all
> * aggregator's ports
> */
> __set_agg_ports_ready(port->aggregator,
> __agg_ports_are_ready(port->aggregator));
>
> ----analysis: port->aggregator is still NULL, which causes problem.
>
>
> aggregator = __get_first_agg(port);
> ad_agg_selection_logic(aggregator, update_slave_arr);
>
> if (!port->aggregator->is_active)
> port->actor_oper_port_state &= ~LACP_STATE_SYNCHRONIZATION;
> }
>
>
> Thanks.
> .
>

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