From: Wei Wang <wei...@google.com> In udp_v4/6_early_demux() code, we try to hold dst->__refcnt for dst with DST_NOCACHE flag. This is because later in udp_sk_rx_dst_set() function, we will try to cache this dst in sk for connected case. However, a better way to achieve this is to not try to hold dst in early_demux(), but in udp_sk_rx_dst_set(), call dst_hold_safe(). This approach is also more consistant with how tcp is handling it. And it will make later changes simpler.
Signed-off-by: Wei Wang <wei...@google.com> Acked-by: Martin KaFai Lau <ka...@fb.com> --- net/ipv4/udp.c | 22 ++++++++++------------ net/ipv6/udp.c | 14 ++++++-------- 2 files changed, 16 insertions(+), 20 deletions(-) diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c index 2bc638c48b86..99fb1fb90ad3 100644 --- a/net/ipv4/udp.c +++ b/net/ipv4/udp.c @@ -1977,9 +1977,10 @@ static void udp_sk_rx_dst_set(struct sock *sk, struct dst_entry *dst) { struct dst_entry *old; - dst_hold(dst); - old = xchg(&sk->sk_rx_dst, dst); - dst_release(old); + if (dst_hold_safe(dst)) { + old = xchg(&sk->sk_rx_dst, dst); + dst_release(old); + } } /* @@ -2302,15 +2303,12 @@ void udp_v4_early_demux(struct sk_buff *skb) if (dst) dst = dst_check(dst, 0); - if (dst) { - /* DST_NOCACHE can not be used without taking a reference */ - if (dst->flags & DST_NOCACHE) { - if (likely(atomic_inc_not_zero(&dst->__refcnt))) - skb_dst_set(skb, dst); - } else { - skb_dst_set_noref(skb, dst); - } - } + if (dst) + /* set noref for now. + * any place which wants to hold dst has to call + * dst_hold_safe() + */ + skb_dst_set_noref(skb, dst); } int udp_rcv(struct sk_buff *skb) diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c index 2e9b52bded2d..a2152e2138ff 100644 --- a/net/ipv6/udp.c +++ b/net/ipv6/udp.c @@ -919,14 +919,12 @@ static void udp_v6_early_demux(struct sk_buff *skb) if (dst) dst = dst_check(dst, inet6_sk(sk)->rx_dst_cookie); - if (dst) { - if (dst->flags & DST_NOCACHE) { - if (likely(atomic_inc_not_zero(&dst->__refcnt))) - skb_dst_set(skb, dst); - } else { - skb_dst_set_noref(skb, dst); - } - } + if (dst) + /* set noref for now. + * any place which wants to hold dst has to call + * dst_hold_safe() + */ + skb_dst_set_noref(skb, dst); } static __inline__ int udpv6_rcv(struct sk_buff *skb) -- 2.13.1.518.g3df882009-goog