net: ethernet: s10hssi: fix the crash in the ipv6 network

v2:
Simplife the implementation of ndo_start_xmit().

v1:
This patch simply fills ndo_start_xmit() in netdev and no other
operations.

In the ipv6 network, after the date is sent, the netdev ndo_start_xmit()
hook will be called. But s10ssi does not fill the ndo_start_xmit() in
netdev, so it will case a "NULL pointer" crash.

In the ipv6 network, run the following command:

$ ifconfig s10hssi0 up

Will cause the machine to crash:

[  961.346621] BUG: unable to handle kernel NULL pointer dereference at 0000000000000000
[  961.346651] PGD 0 P4D 0
[  961.346661] Oops: 0010 [#1] SMP NOPTI
[  961.346673] CPU: 62 PID: 0 Comm: swapper/62 Kdump: loaded Tainted: G           OE    --------- -  -
[  961.346702] Hardware name: Inspur SA5212M5/YZMB-00882-104, BIOS 4.1.8 05/21/2019
[  961.346721] RIP: 0010:          (null)
[  961.346734] Code: Bad RIP value.
[  961.346745] RSP: 0018:ffff98ce7fb83bd0 EFLAGS: 00010286
[  961.346760] RAX: 0000000000000000 RBX: ffff988e7fff6000 RCX: ffff98ce7fb83c4c
[  961.346778] RDX: ffffffffc0479620 RSI: ffff988e7fff6000 RDI: ffff98ce7e3ce900
[  961.346796] RBP: 00000000ee0f0000 R08: 0000000000000000 R09: 000000000000004c
[  961.346815] R10: ffff988e7cd9e540 R11: 0000000000000000 R12: 0000000000000000
[  961.346833] R13: ffff985d88f61000 R14: ffff988e6975ce00 R15: ffff98ce7e3ce900
[  961.346851] FS:  0000000000000000(0000) GS:ffff98ce7fb80000(0000) knlGS:0000000000000000
[  961.346871] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  961.346887] CR2: ffffffffffffffd6 CR3: 0000000e8880a006 CR4: 00000000007606e0
[  961.346905] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[  961.346924] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[  961.346943] PKRU: 55555554
[  961.346953] Call Trace:
[  961.346964]  <IRQ>
[  961.346979]  ? dev_hard_start_xmit+0xa5/0x210
[  961.346994]  ? __dev_queue_xmit+0x6c1/0x9e0
[  961.347008]  ? __neigh_create+0x427/0x580
[  961.347023]  ? ip6_finish_output2+0x1b9/0x5b0
[  961.347039]  ? kmem_cache_alloc+0x18e/0x1c0
[  961.347053]  ? kmem_cache_alloc_trace+0x3f/0x1d0
[  961.347068]  ? ip6_output+0x68/0x110
[  961.347083]  ? mld_sendpack+0x168/0x280
[  961.347096]  ? add_grhead.isra.26+0x2e/0xa0
[  961.347110]  ? mld_ifc_timer_expire+0x198/0x2d0
[  961.347125]  ? mld_clear_delrec+0xf0/0xf0
[  961.347142]  ? call_timer_fn+0x2b/0x130
[  961.347154]  ? run_timer_softirq+0x3d1/0x410
[  961.347168]  ? enqueue_hrtimer+0x38/0x90
[  961.347182]  ? __hrtimer_run_queues+0x130/0x280
[  961.347198]  ? __do_softirq+0xe3/0x30a
[  961.347211]  ? ktime_get+0x36/0xa0
[  961.347225]  ? irq_exit+0x100/0x110
[  961.347237]  ? smp_apic_timer_interrupt+0x74/0x140
[  961.347252]  ? apic_timer_interrupt+0xf/0x20
[  961.347264]  </IRQ>
[  961.347275]  ? mwait_idle+0x7d/0x160
[  961.347764]  ? do_idle+0x1f1/0x280
[  961.348207]  ? cpu_startup_entry+0x6f/0x80
[  961.348649]  ? start_secondary+0x1a7/0x200
[  961.349081]  ? secondary_startup_64+0xb7/0xc0

Signed-off-by: Chen Guanqiao <chenguanqiao@kuaishou.com>

Author: Chen Guanqiao

drivers/net/ethernet/intel/s10hssi.c

@@ -161,10 +161,17 @@ static int netdev_set_mac_address(struct net_device *ndev, void *p)
 	return 0;
 }
 
+static netdev_tx_t s10hssi_dummy_netdev_xmit(struct sk_buff *skb,
+					     struct net_device *dev)
+{
+	return NETDEV_TX_OK;
+}
+
 static const struct net_device_ops netdev_ops = {
 	.ndo_change_mtu = netdev_change_mtu,
 	.ndo_set_features = netdev_set_features,
 	.ndo_set_mac_address = netdev_set_mac_address,
+	.ndo_start_xmit = s10hssi_dummy_netdev_xmit,
 };
 
 struct stat_info {