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Message-ID: <CALCETrU2kFYsYnhPnBWd3059k5Z6=8B==kwXU0xidAsR6EqgCg@mail.gmail.com>
Date:	Fri, 9 Jan 2015 11:43:26 -0800
From:	Andy Lutomirski <luto@...capital.net>
To:	Willem de Bruijn <willemb@...gle.com>
Cc:	Network Development <netdev@...r.kernel.org>,
	"David S. Miller" <davem@...emloft.net>,
	Richard Cochran <richardcochran@...il.com>,
	Eric Dumazet <eric.dumazet@...il.com>
Subject: Re: [PATCH net-next RFC 1/5] net-timestamp: no-payload option

On Fri, Jan 9, 2015 at 9:31 AM, Willem de Bruijn <willemb@...gle.com> wrote:
> From: Willem de Bruijn <willemb@...gle.com>
>
> Add timestamping option SOF_TIMESTAMPING_OPT_TSONLY. For transmit
> timestamps, this loops timestamps on top of empty packets.
>
> Doing so reduces the pressure on SO_RCVBUF. Payload inspection and
> cmsg reception (aside from timestamps) are no longer possible. This
> works together with a follow on patch that allows administrators to
> only allow tx timestamping if it does not loop payload or metadata.

If this loses IP_PKTINFO, that will be a bit unfortunate.

--Andy

>
> Signed-off-by: Willem de Bruijn <willemb@...gle.com>
> ---
>  include/uapi/linux/net_tstamp.h |  3 ++-
>  net/core/skbuff.c               | 19 ++++++++++++++-----
>  net/ipv4/ip_sockglue.c          |  9 +++++----
>  net/ipv6/datagram.c             |  4 ++--
>  net/rxrpc/ar-error.c            |  5 +++++
>  5 files changed, 28 insertions(+), 12 deletions(-)
>
> diff --git a/include/uapi/linux/net_tstamp.h b/include/uapi/linux/net_tstamp.h
> index edbc888..6d1abea 100644
> --- a/include/uapi/linux/net_tstamp.h
> +++ b/include/uapi/linux/net_tstamp.h
> @@ -24,8 +24,9 @@ enum {
>         SOF_TIMESTAMPING_TX_SCHED = (1<<8),
>         SOF_TIMESTAMPING_TX_ACK = (1<<9),
>         SOF_TIMESTAMPING_OPT_CMSG = (1<<10),
> +       SOF_TIMESTAMPING_OPT_TSONLY = (1<<11),
>
> -       SOF_TIMESTAMPING_LAST = SOF_TIMESTAMPING_OPT_CMSG,
> +       SOF_TIMESTAMPING_LAST = SOF_TIMESTAMPING_OPT_TSONLY,
>         SOF_TIMESTAMPING_MASK = (SOF_TIMESTAMPING_LAST - 1) |
>                                  SOF_TIMESTAMPING_LAST
>  };
> diff --git a/net/core/skbuff.c b/net/core/skbuff.c
> index 5a2a2e8..ece2bb8 100644
> --- a/net/core/skbuff.c
> +++ b/net/core/skbuff.c
> @@ -3710,19 +3710,28 @@ void __skb_tstamp_tx(struct sk_buff *orig_skb,
>                      struct sock *sk, int tstype)
>  {
>         struct sk_buff *skb;
> +       bool tsonly = sk->sk_tsflags & SOF_TIMESTAMPING_OPT_TSONLY;
>
>         if (!sk)
>                 return;
>
> -       if (hwtstamps)
> -               *skb_hwtstamps(orig_skb) = *hwtstamps;
> +       if (tsonly)
> +               skb = alloc_skb(0, GFP_ATOMIC);
>         else
> -               orig_skb->tstamp = ktime_get_real();
> -
> -       skb = skb_clone(orig_skb, GFP_ATOMIC);
> +               skb = skb_clone(orig_skb, GFP_ATOMIC);
>         if (!skb)
>                 return;
>
> +       if (tsonly) {
> +               skb_shinfo(skb)->tx_flags = skb_shinfo(orig_skb)->tx_flags;
> +               skb_shinfo(skb)->tskey = skb_shinfo(orig_skb)->tskey;
> +       }
> +
> +       if (hwtstamps)
> +               *skb_hwtstamps(skb) = *hwtstamps;
> +       else
> +               skb->tstamp = ktime_get_real();
> +
>         __skb_complete_tx_timestamp(skb, sk, tstype);
>  }
>  EXPORT_SYMBOL_GPL(__skb_tstamp_tx);
> diff --git a/net/ipv4/ip_sockglue.c b/net/ipv4/ip_sockglue.c
> index a317797..d81ef70 100644
> --- a/net/ipv4/ip_sockglue.c
> +++ b/net/ipv4/ip_sockglue.c
> @@ -440,7 +440,7 @@ static bool ipv4_pktinfo_prepare_errqueue(const struct sock *sk,
>
>         if ((ee_origin != SO_EE_ORIGIN_TIMESTAMPING) ||
>             (!(sk->sk_tsflags & SOF_TIMESTAMPING_OPT_CMSG)) ||
> -           (!skb->dev))
> +           (!skb->dev) || (!skb->len))
>                 return false;
>
>         info->ipi_spec_dst.s_addr = ip_hdr(skb)->saddr;
> @@ -483,7 +483,7 @@ int ip_recv_error(struct sock *sk, struct msghdr *msg, int len, int *addr_len)
>
>         serr = SKB_EXT_ERR(skb);
>
> -       if (sin) {
> +       if (sin && skb->len) {
>                 sin->sin_family = AF_INET;
>                 sin->sin_addr.s_addr = *(__be32 *)(skb_network_header(skb) +
>                                                    serr->addr_offset);
> @@ -496,8 +496,9 @@ int ip_recv_error(struct sock *sk, struct msghdr *msg, int len, int *addr_len)
>         sin = &errhdr.offender;
>         sin->sin_family = AF_UNSPEC;
>
> -       if (serr->ee.ee_origin == SO_EE_ORIGIN_ICMP ||
> -           ipv4_pktinfo_prepare_errqueue(sk, skb, serr->ee.ee_origin)) {
> +       if (skb->len &&
> +           (serr->ee.ee_origin == SO_EE_ORIGIN_ICMP ||
> +            ipv4_pktinfo_prepare_errqueue(sk, skb, serr->ee.ee_origin))) {
>                 struct inet_sock *inet = inet_sk(sk);
>
>                 sin->sin_family = AF_INET;
> diff --git a/net/ipv6/datagram.c b/net/ipv6/datagram.c
> index 100c589..91a31ea 100644
> --- a/net/ipv6/datagram.c
> +++ b/net/ipv6/datagram.c
> @@ -369,7 +369,7 @@ int ipv6_recv_error(struct sock *sk, struct msghdr *msg, int len, int *addr_len)
>
>         serr = SKB_EXT_ERR(skb);
>
> -       if (sin) {
> +       if (sin && skb->len) {
>                 const unsigned char *nh = skb_network_header(skb);
>                 sin->sin6_family = AF_INET6;
>                 sin->sin6_flowinfo = 0;
> @@ -394,7 +394,7 @@ int ipv6_recv_error(struct sock *sk, struct msghdr *msg, int len, int *addr_len)
>         memcpy(&errhdr.ee, &serr->ee, sizeof(struct sock_extended_err));
>         sin = &errhdr.offender;
>         sin->sin6_family = AF_UNSPEC;
> -       if (serr->ee.ee_origin != SO_EE_ORIGIN_LOCAL) {
> +       if (serr->ee.ee_origin != SO_EE_ORIGIN_LOCAL && skb->len) {
>                 sin->sin6_family = AF_INET6;
>                 sin->sin6_flowinfo = 0;
>                 sin->sin6_port = 0;
> diff --git a/net/rxrpc/ar-error.c b/net/rxrpc/ar-error.c
> index 74c0fcd..5394b6b 100644
> --- a/net/rxrpc/ar-error.c
> +++ b/net/rxrpc/ar-error.c
> @@ -42,6 +42,11 @@ void rxrpc_UDP_error_report(struct sock *sk)
>                 _leave("UDP socket errqueue empty");
>                 return;
>         }
> +       if (!skb->len) {
> +               _leave("UDP empty message");
> +               kfree_skb(skb);
> +               return;
> +       }
>
>         rxrpc_new_skb(skb);
>
> --
> 2.2.0.rc0.207.ga3a616c
>



-- 
Andy Lutomirski
AMA Capital Management, LLC
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