s390/qeth: Fix potential loss of L3-IP@ in case of network issues

Symptom:
In case of a bad cable connection (e.g. dirty optics) a fast sequence of
network DOWN-UP-DOWN-UP could happen. UP triggers recovery of the qeth
interface. In case of a second DOWN while recovery is still ongoing, it
can happen that the IP@ of a Layer3 qeth interface is lost and will not
be recovered by the second UP.

Problem:
When registration of IP addresses with Layer 3 qeth devices fails, (e.g.
because of bad address format) the respective IP address is deleted from
its hash-table in the driver. If registration fails because of a ENETDOWN
condition, the address should stay in the hashtable, so a subsequent
recovery can restore it.

3caa4af834df ("qeth: keep ip-address after LAN_OFFLINE failure")
fixes this for registration failures during normal operation, but not
during recovery.

Solution:
Keep L3-IP address in case of ENETDOWN in qeth_l3_recover_ip(). For
consistency with qeth_l3_add_ip() we also keep it in case of EADDRINUSE,
i.e. for some reason the card already/still has this address registered.

Fixes: 4a71df50047f ("qeth: new qeth device driver")
Cc: stable@vger.kernel.org
Signed-off-by: Alexandra Winter <wintera@linux.ibm.com>
Link: https://lore.kernel.org/r/20240206085849.2902775-1-wintera@linux.ibm.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

diff --git a/drivers/s390/net/qeth_l3_main.c b/drivers/s390/net/qeth_l3_main.c
index b92a32b4b1141670cc2f3c2e8b91a8e1d526b26a..04c64ce0a1ca1a2006d31ca5c7ee819598f155c4 100644 (file)
--- a/drivers/s390/net/qeth_l3_main.c
+++ b/drivers/s390/net/qeth_l3_main.c
@@ -255,9 +255,10 @@ static void qeth_l3_clear_ip_htable(struct qeth_card *card, int recover)
                if (!recover) {
                        hash_del(&addr->hnode);
                        kfree(addr);
-                       continue;
+               } else {
+                       /* prepare for recovery */
+                       addr->disp_flag = QETH_DISP_ADDR_ADD;
                }
-               addr->disp_flag = QETH_DISP_ADDR_ADD;
        }
 
        mutex_unlock(&card->ip_lock);
@@ -278,9 +279,11 @@ static void qeth_l3_recover_ip(struct qeth_card *card)
                if (addr->disp_flag == QETH_DISP_ADDR_ADD) {
                        rc = qeth_l3_register_addr_entry(card, addr);
 
-                       if (!rc) {
+                       if (!rc || rc == -EADDRINUSE || rc == -ENETDOWN) {
+                               /* keep it in the records */
                                addr->disp_flag = QETH_DISP_ADDR_DO_NOTHING;
                        } else {
+                               /* bad address */
                                hash_del(&addr->hnode);
                                kfree(addr);
                        }