[PATCH net 2/4] s390/qeth: don't use obsolete dst entry

Julian Wiedmann
2019-06-03T15:04:44Z

While qeth_l3 uses netif_keep_dst() to hold onto the dst, a skb's dst
may still have been obsoleted (via dst_dev_put()) by the time that we
end up using it. The dst then points to the loopback interface, which
means the neighbour lookup in qeth_l3_get_cast_type() determines a bogus
cast type of RTN_BROADCAST.
For IQD interfaces this causes us to place such skbs on the wrong
HW queue, resulting in TX errors.

Fix-up the various call sites to check whether the dst is obsolete, and
fall back accordingly.

Signed-off-by: Julian Wiedmann <jwi@linux.ibm.com>
---
drivers/s390/net/qeth_core.h | 2 +-
drivers/s390/net/qeth_l3_main.c | 57 ++++++++++++++++++++-------------
2 files changed, 36 insertions(+), 23 deletions(-)

diff --git a/drivers/s390/net/qeth_core.h b/drivers/s390/net/qeth_core.h
index 784a2e76a1b0..f89f5b0a9805 100644
--- a/drivers/s390/net/qeth_core.h
+++ b/drivers/s390/net/qeth_core.h
@@ -275,7 +275,7 @@ struct qeth_hdr_layer3 {
struct in6_addr ipv6_addr;
struct ipv4 {
u8 res[12];
- u32 addr;
+ __be32 addr;
} ipv4;
/* RX: */
struct rx {
diff --git a/drivers/s390/net/qeth_l3_main.c b/drivers/s390/net/qeth_l3_main.c
index 2df67abdfde7..93bcfc272f20 100644
--- a/drivers/s390/net/qeth_l3_main.c
+++ b/drivers/s390/net/qeth_l3_main.c
@@ -1893,8 +1893,9 @@ static int qeth_l3_get_cast_type(struct sk_buff *skb)

rcu_read_lock();
dst = skb_dst(skb);
- if (dst)
+ if (dst && dst->obsolete <= 0)
n = dst_neigh_lookup_skb(dst, skb);
+
if (n) {
int cast_type = n->type;

@@ -1924,6 +1925,33 @@ static int qeth_l3_get_cast_type(struct sk_buff *skb)
}
}

+static void qeth_l3_get_next_hop_v4(struct sk_buff *skb, __be32 *next_hop)
+{
+ struct rtable *rt;
+
+ rcu_read_lock();
+ rt = skb_rtable(skb);
+ if (rt && rt->dst.obsolete <= 0)
+ *next_hop = rt_nexthop(rt, ip_hdr(skb)->daddr);
+ else
+ *next_hop = ip_hdr(skb)->daddr;
+ rcu_read_unlock();
+}
+
+static void qeth_l3_get_next_hop_v6(struct sk_buff *skb,
+ struct in6_addr *next_hop)
+{
+ const struct rt6_info *rt;
+
+ rcu_read_lock();
+ rt = skb_rt6_info(skb);
+ if (rt && rt->dst.obsolete <= 0 && !ipv6_addr_any(&rt->rt6i_gateway))
+ *next_hop = rt->rt6i_gateway;
+ else
+ *next_hop = ipv6_hdr(skb)->daddr;
+ rcu_read_unlock();
+}
+
static u8 qeth_l3_cast_type_to_flag(int cast_type)
{
if (cast_type == RTN_MULTICAST)
@@ -1980,33 +2008,18 @@ static void qeth_l3_fill_header(struct qeth_qdio_out_q *queue,

l3_hdr->flags = qeth_l3_cast_type_to_flag(cast_type);

- /* OSA only: */
- if (!ipv) {
- l3_hdr->flags |= QETH_HDR_PASSTHRU;
- return;
- }
-
- rcu_read_lock();
if (ipv == 4) {
- struct rtable *rt = skb_rtable(skb);
-
- *((__be32 *) &hdr->hdr.l3.next_hop.ipv4.addr) = (rt) ?
- rt_nexthop(rt, ip_hdr(skb)->daddr) :
- ip_hdr(skb)->daddr;
- } else {
- /* IPv6 */
- const struct rt6_info *rt = skb_rt6_info(skb);
-
- if (rt && !ipv6_addr_any(&rt->rt6i_gateway))
- l3_hdr->next_hop.ipv6_addr = rt->rt6i_gateway;
- else
- l3_hdr->next_hop.ipv6_addr = ipv6_hdr(skb)->daddr;
+ qeth_l3_get_next_hop_v4(skb, &l3_hdr->next_hop.ipv4.addr);
+ } else if (ipv == 6) {
+ qeth_l3_get_next_hop_v6(skb, &l3_hdr->next_hop.ipv6_addr);

hdr->hdr.l3.flags |= QETH_HDR_IPV6;
if (!IS_IQD(card))
hdr->hdr.l3.flags |= QETH_HDR_PASSTHRU;
+ } else {
+ /* OSA only */
+ l3_hdr->flags |= QETH_HDR_PASSTHRU;
}
- rcu_read_unlock();
}

static void qeth_l3_fixup_headers(struct sk_buff *skb)
--
2.17.1