[PATCH 5.12 232/296] net: packetmmap: fix only tx timestamp on request

Greg Kroah-Hartman
2021-05-31T16:41:12Z

From: Richard Sanger <rsanger@wand.net.nz>

[ Upstream commit 171c3b151118a2fe0fc1e2a9d1b5a1570cfe82d2 ]

The packetmmap tx ring should only return timestamps if requested via
setsockopt PACKET_TIMESTAMP, as documented. This allows compatibility
with non-timestamp aware user-space code which checks
tp_status == TP_STATUS_AVAILABLE; not expecting additional timestamp
flags to be set in tp_status.

Fixes: b9c32fb27170 ("packet: if hw/sw ts enabled in rx/tx ring, report which ts we got")
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: Willem de Bruijn <willemdebruijn.kernel@gmail.com>
Signed-off-by: Richard Sanger <rsanger@wand.net.nz>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/packet/af_packet.c | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index 9611e41c7b8b..c52557ec7fb3 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -422,7 +422,8 @@ static __u32 tpacket_get_timestamp(struct sk_buff *skb, struct timespec64 *ts,
ktime_to_timespec64_cond(shhwtstamps->hwtstamp, ts))
return TP_STATUS_TS_RAW_HARDWARE;

- if (ktime_to_timespec64_cond(skb->tstamp, ts))
+ if ((flags & SOF_TIMESTAMPING_SOFTWARE) &&
+ ktime_to_timespec64_cond(skb->tstamp, ts))
return TP_STATUS_TS_SOFTWARE;

return 0;
@@ -2340,7 +2341,12 @@ static int tpacket_rcv(struct sk_buff *skb, struct net_device *dev,

skb_copy_bits(skb, 0, h.raw + macoff, snaplen);

- if (!(ts_status = tpacket_get_timestamp(skb, &ts, po->tp_tstamp)))
+ /* Always timestamp; prefer an existing software timestamp taken
+ * closer to the time of capture.
+ */
+ ts_status = tpacket_get_timestamp(skb, &ts,
+ po->tp_tstamp | SOF_TIMESTAMPING_SOFTWARE);
+ if (!ts_status)
ktime_get_real_ts64(&ts);

status |= ts_status;
--
2.30.2