netdev - [PATCH 1/1] af_packet: don't enable timestamps in mmap'ed sockets

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Date:	Thu, 09 Aug 2007 16:21:54 +0200
From:	Unai Uribarri <unai.uribarri@...enet.com>
To:	netdev@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org
Subject: [PATCH 1/1] af_packet: don't enable timestamps in mmap'ed sockets

Hello folks,

I've discovered two strange behaviours (bugs?) about timestamp
generation:

1. If a program opens an AF_PACKET socket and setup a reception ring
with setsockopt(sock, SOL_PACKET, PACKET_RX_RING), timestamps are
automatically (re)enabled at the reception of every packet.

2. Setting SOL_SOCKET/SO_TIMESTAMP to 0 doesn't disables timestamp
generation. Every skb continues begin timestamped until you close the
socket that activated it.

Timestamp generation is a heavy task that is consuming more than 50% of
the CPU (using ACPI PM clock) and is currently the bottleneck in my
packet capturing application.

The attached patch removes the automatic timestamp activation, that
only mmap'ed AF_PACKET sockets perform. I known it can break user
applications, but I believe that it's the correct solution.

I will be very pleased to receive any feedback.

Signed-off-by: Unai Uribarri <unai.uribarri@...enet.com>

---

diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index 1322d62..a4f2da3 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -640,10 +640,6 @@ static int tpacket_rcv(struct sk_buff *skb, struct net_device *dev, struct packe
        h->tp_snaplen = snaplen;
        h->tp_mac = macoff;
        h->tp_net = netoff;
-       if (skb->tstamp.tv64 == 0) {
-               __net_timestamp(skb);
-               sock_enable_timestamp(sk);
-       }
        tv = ktime_to_timeval(skb->tstamp);
        h->tp_sec = tv.tv_sec;
        h->tp_usec = tv.tv_usec;

-
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html