udp: fix rx queue len reported by diag and proc interface
After commit 6b229cf77d68 ("udp: add batching to udp_rmem_release()")
the sk_rmem_alloc field does not measure exactly anymore the
receive queue length, because we batch the rmem release. The issue
is really apparent only after commit 0d4a6608f68c ("udp: do rmem bulk
free even if the rx sk queue is empty"): the user space can easily
check for an empty socket with not-0 queue length reported by the 'ss'
tool or the procfs interface.
We need to use a custom UDP helper to report the correct queue length,
taking into account the forward allocation deficit.
Reported-by: trevor.francis@46labs.com
Fixes: 6b229cf77d68 ("UDP: add batching to udp_rmem_release()")
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/net/udp.h b/include/net/udp.h
index 7ba0ed2..b1ea8b0 100644
--- a/include/net/udp.h
+++ b/include/net/udp.h
@@ -247,6 +247,11 @@ static inline __be16 udp_flow_src_port(struct net *net, struct sk_buff *skb,
return htons((((u64) hash * (max - min)) >> 32) + min);
}
+static inline int udp_rqueue_get(struct sock *sk)
+{
+ return sk_rmem_alloc_get(sk) - READ_ONCE(udp_sk(sk)->forward_deficit);
+}
+
/* net/ipv4/udp.c */
void udp_destruct_sock(struct sock *sk);
void skb_consume_udp(struct sock *sk, struct sk_buff *skb, int len);