Re: [PATCH net-next 1/1] net sched actions: mirred add support for setting Dst MAC address

Nikolay Aleksandrov
2016-07-02T13:49:42Z

On 02/07/16 15:26, Jamal Hadi Salim wrote:
> From: Jamal Hadi Salim <jhs@mojatatu.com>
>
> Often redirecting or mirroring requires that we set the MAC address
> of the target device. While it is possible to pipe to a pedit action
> this obsoletes the need for that. This is justified feature because
> the dst MAC addresses rewrite is such a common use case.
>
> Sample usage:
> sudo $TC filter add dev $ETH parent 1: protocol ip prio 10 \
> u32 match ip protocol 1 0xff flowid 1:2 \
> action mirred egress redirect dev $SPANPORT dst 02:15:15:15:15:15
>
> This will match all icmp packets going out on dev $ETH and
> redirect them to dev $SPANPORT while setting their dst MAC address
> to 02:15:15:15:15:15
>
> Signed-off-by: Jamal Hadi Salim <jhs@mojatatu.com>
> ---
> include/net/tc_act/tc_mirred.h | 4 +++-
> include/uapi/linux/tc_act/tc_mirred.h | 7 ++++---
> net/sched/act_mirred.c | 20 +++++++++++++++++++-
> 3 files changed, 26 insertions(+), 5 deletions(-)
>
> diff --git a/include/net/tc_act/tc_mirred.h b/include/net/tc_act/tc_mirred.h
> index e891835..7e8bced 100644
> --- a/include/net/tc_act/tc_mirred.h
> +++ b/include/net/tc_act/tc_mirred.h
> @@ -6,10 +6,12 @@
>
> struct tcf_mirred {
> struct tcf_common common;
> + struct net_device __rcu *tcfm_dev;
> int tcfm_eaction;
> int tcfm_ifindex;
> int tcfm_ok_push;
> - struct net_device __rcu *tcfm_dev;
> + u8 eth_dst[ETH_ALEN];
> + /* XXX 6 bytes hole here*/
> struct list_head tcfm_list;
> };
> #define to_mirred(a) \
> diff --git a/include/uapi/linux/tc_act/tc_mirred.h b/include/uapi/linux/tc_act/tc_mirred.h
> index 3d7a2b3..aaca1ff 100644
> --- a/include/uapi/linux/tc_act/tc_mirred.h
> +++ b/include/uapi/linux/tc_act/tc_mirred.h
> @@ -9,20 +9,21 @@
> #define TCA_EGRESS_MIRROR 2 /* mirror packet to EGRESS */
> #define TCA_INGRESS_REDIR 3 /* packet redirect to INGRESS*/
> #define TCA_INGRESS_MIRROR 4 /* mirror packet to INGRESS */
> -
> +
> struct tc_mirred {
> tc_gen;
> int eaction; /* one of IN/EGRESS_MIRROR/REDIR */
> __u32 ifindex; /* ifindex of egress port */
> };
> -
> +
> enum {
> TCA_MIRRED_UNSPEC,
> TCA_MIRRED_TM,
> TCA_MIRRED_PARMS,
> TCA_MIRRED_PAD,
> + TCA_MIRRED_DMAC,

Hi Jamal,
I think you should update "mirred_policy" in order to ensure that the attribute has
the minimum length for a mac address. Also a minor suggestion - maybe err out on a
zero mac address, otherwise the user might think the operation was successful.

Cheers,
Nik

> __TCA_MIRRED_MAX
> };
> #define TCA_MIRRED_MAX (__TCA_MIRRED_MAX - 1)
> -
> +
> #endif
> diff --git a/net/sched/act_mirred.c b/net/sched/act_mirred.c
> index 5b135d3..044648d 100644
> --- a/net/sched/act_mirred.c
> +++ b/net/sched/act_mirred.c
> @@ -64,15 +64,21 @@ static int tcf_mirred_init(struct net *net, struct nlattr *nla,
> struct net_device *dev;
> int ret, ok_push = 0;
> bool exists = false;
> + u8 *daddr = NULL;
>
> if (nla == NULL)
> return -EINVAL;
> +
> ret = nla_parse_nested(tb, TCA_MIRRED_MAX, nla, mirred_policy);
> if (ret < 0)
> return ret;
> +
> if (tb[TCA_MIRRED_PARMS] == NULL)
> return -EINVAL;
> +
> parm = nla_data(tb[TCA_MIRRED_PARMS]);
> + if (tb[TCA_MIRRED_DMAC])
> + daddr = nla_data(tb[TCA_MIRRED_DMAC]);
>
> exists = tcf_hash_check(tn, parm->index, a, bind);
> if (exists && bind)
> @@ -126,6 +132,9 @@ static int tcf_mirred_init(struct net *net, struct nlattr *nla,
> }
> m = to_mirred(a);
>
> + if (daddr)
> + ether_addr_copy(m->eth_dst, daddr);
> +
> ASSERT_RTNL();
> m->tcf_action = parm->action;
> m->tcfm_eaction = parm->eaction;
> @@ -190,6 +199,9 @@ static int tcf_mirred(struct sk_buff *skb, const struct tc_action *a,
>
> skb2->skb_iif = skb->dev->ifindex;
> skb2->dev = dev;
> + if (!is_zero_ether_addr(m->eth_dst))
> + ether_addr_copy(eth_hdr(skb2)->h_dest, m->eth_dst);
> +
> err = dev_queue_xmit(skb2);
>
> if (err) {
> @@ -203,7 +215,8 @@ out:
> return retval;
> }
>
> -static int tcf_mirred_dump(struct sk_buff *skb, struct tc_action *a, int bind, int ref)
> +static int tcf_mirred_dump(struct sk_buff *skb, struct tc_action *a, int bind,
> + int ref)
> {
> unsigned char *b = skb_tail_pointer(skb);
> struct tcf_mirred *m = a->priv;
> @@ -220,6 +233,11 @@ static int tcf_mirred_dump(struct sk_buff *skb, struct tc_action *a, int bind, i
> if (nla_put(skb, TCA_MIRRED_PARMS, sizeof(opt), &opt))
> goto nla_put_failure;
>
> + if (!is_zero_ether_addr(m->eth_dst)) {
> + if (nla_put(skb, TCA_MIRRED_DMAC, ETH_ALEN, m->eth_dst))
> + goto nla_put_failure;
> + }
> +
> tcf_tm_dump(&t, &m->tcf_tm);
> if (nla_put_64bit(skb, TCA_MIRRED_TM, sizeof(t), &t, TCA_MIRRED_PAD))
> goto nla_put_failure;
>