Re: [PATCH] net/tap: add support for fixed mac addresses

[Pascal Mazon <pascal.mazon@6wind.com>]

On Tue, 11 Apr 2017 13:23:24 +0000
"Wiles, Keith" <keith.wiles@intel.com> wrote:

> 
> > On Apr 11, 2017, at 2:18 AM, Pascal Mazon <pascal.mazon@6wind.com> wrote:
> > 
> > Hi Keith,
> > 
> > I have a few comments on your patch, see inline.
> > 
> > On Mon, 10 Apr 2017 13:18:50 -0500
> > Keith Wiles <keith.wiles@intel.com> wrote:
> > 
> >> Support for a fixed MAC address for testing with the last octet
> >> incrementing by one for each interface defined with the new 'mac=fixed'
> >> string on the --vdev option. The default option is still to randomize
> >> the MAC address for each tap interface.
> >> 
> >> Signed-off-by: Keith Wiles <keith.wiles@intel.com>
> >> ---
> >> doc/guides/nics/tap.rst       | 13 +++++++++++-
> >> drivers/net/tap/rte_eth_tap.c | 49 ++++++++++++++++++++++++++++++++++++++++---
> >> 2 files changed, 58 insertions(+), 4 deletions(-)
> >> 
> >> diff --git a/doc/guides/nics/tap.rst b/doc/guides/nics/tap.rst
> >> index 5c5ba5357..e3819836a 100644
> >> --- a/doc/guides/nics/tap.rst
> >> +++ b/doc/guides/nics/tap.rst
> >> @@ -46,7 +46,7 @@ These TAP interfaces can be used with Wireshark or tcpdump or Pktgen-DPDK
> >> along with being able to be used as a network connection to the DPDK
> >> application. The method enable one or more interfaces is to use the
> >> ``--vdev=net_tap0`` option on the DPDK application command line. Each
> >> -``--vdev=net_tap1`` option give will create an interface named dtap0, dtap1,
> >> +``--vdev=net_tap1`` option given will create an interface named dtap0, dtap1,
> >> and so on.
> >> 
> >> The interface name can be changed by adding the ``iface=foo0``, for example::
> >> @@ -58,6 +58,17 @@ needed, but the interface does not enforce that speed, for example::
> >> 
> >>    --vdev=net_tap0,iface=foo0,speed=25000
> >> 
> >> +Normally the PMD will generate random MAC address, but when testing or with
> > 
> > "random MAC" -> "a random MAC"
> > 
> >> +a static configurations the developer may need a fixed MAC address style.
> > 
> > "configurations" -> "configuration"
> > 
> >> +Using the option ``mac=fixed`` you can create a fixed known MAC address::
> >> +
> >> +   --vdev=net_tap0,mac=fixed
> >> +
> >> +The MAC address will be fixed value with the last octet incrementing by one
> > 
> > "be" -> "have a"
> > 
> >> +each time for each interface string containing ``mac=fixed``. The MAC address
> > 
> > "each time" -> ""
> > 
> >> +is formatted as 00:'d':'t':'a':'p':[00-FF] convert the characters to hex
> > 
> > " convert" -> ". Convert"
> > 
> >> +and you get ``00:64:74:61:70:[00-FF]``.
> >> +
> >> It is possible to specify a remote netdevice to capture packets from by adding
> >> ``remote=foo1``, for example::
> >> 
> >> diff --git a/drivers/net/tap/rte_eth_tap.c b/drivers/net/tap/rte_eth_tap.c
> >> index 347a80741..7a676c588 100644
> >> --- a/drivers/net/tap/rte_eth_tap.c
> >> +++ b/drivers/net/tap/rte_eth_tap.c
> >> @@ -1,7 +1,7 @@
> >> /*-
> >>  *   BSD LICENSE
> >>  *
> >> - *   Copyright(c) 2016 Intel Corporation. All rights reserved.
> >> + *   Copyright(c) 2017 Intel Corporation. All rights reserved.
> > 
> > Shouldn't it be "2016-2017"?
> > 
> >>  *   All rights reserved.
> >>  *
> >>  *   Redistribution and use in source and binary forms, with or without
> >> @@ -71,6 +71,13 @@
> >> #define ETH_TAP_IFACE_ARG       "iface"
> >> #define ETH_TAP_SPEED_ARG       "speed"
> >> #define ETH_TAP_REMOTE_ARG      "remote"
> >> +#define ETH_TAP_MAC_ARG		"mac"
> > 
> > You used tabs instead of spaces.
> > 
> >> +
> >> +#ifdef IFF_MULTI_QUEUE
> >> +#define RTE_PMD_TAP_MAX_QUEUES	16
> >> +#else
> >> +#define RTE_PMD_TAP_MAX_QUEUES	1
> >> +#endif
> > 
> > Remove this IFF_MULTI_QUEUE definition as it is done in rte_eth_tap.h now (needed for pmd_internals).
> 
> This should have been removed in your patch and now that Ferruh wants you to submit a patch for the string at the bottom of the PMD, can you remove it?
> 
> I can do both in my patch, but Ferruh and you need to agree before I can submit my patch.

Ferruh details how it's been integrated in next-net, nothing to add there :)

> 
> > 
> >> 
> >> #define FLOWER_KERNEL_VERSION KERNEL_VERSION(4, 2, 0)
> >> #define FLOWER_VLAN_KERNEL_VERSION KERNEL_VERSION(4, 9, 0)
> >> @@ -81,10 +88,12 @@ static const char *valid_arguments[] = {
> >> 	ETH_TAP_IFACE_ARG,
> >> 	ETH_TAP_SPEED_ARG,
> >> 	ETH_TAP_REMOTE_ARG,
> >> +	ETH_TAP_MAC_ARG,
> >> 	NULL
> >> };
> >> 
> >> static int tap_unit;
> >> +static int fixed_mac_type;
> > 
> > There is no need for a global variable, especially as the value should not be the same for each driver instance.
> > Typically when one tap uses "mac=fixed" and the next one doesn't.
> > More comments bellow for that.
> > 
> >> 
> >> static volatile uint32_t tap_trigger;	/* Rx trigger */
> >> 
> >> @@ -1230,7 +1239,17 @@ eth_dev_tap_create(const char *name, char *tap_name, char *remote_iface)
> >> 		rte_memcpy(&pmd->eth_addr, ifr.ifr_hwaddr.sa_data,
> >> 			   ETHER_ADDR_LEN);
> >> 	} else {
> >> -		eth_random_addr((uint8_t *)&pmd->eth_addr);
> >> +		if (fixed_mac_type) {
> >> +			static int iface_idx;

I'd suggest using something like this, as there's no need for so much lines to do the same:

char mac[ETHER_ADDR_LEN] = "\x00\x64\x74\x61\x70\x00"; /* 0:d:t:a:p:0 */

mac[ETHER_ADDR_LEN-1] = iface_idx++;
rte_memcpy(&pmd->eth_addr, mac, ETHER_ADDR_LEN);


> >> +
> >> +			pmd->eth_addr.addr_bytes[0] = 0x00;
> >> +			pmd->eth_addr.addr_bytes[1] = 'd';
> >> +			pmd->eth_addr.addr_bytes[2] = 't';
> >> +			pmd->eth_addr.addr_bytes[3] = 'a';
> >> +			pmd->eth_addr.addr_bytes[4] = 'p';
> >> +			pmd->eth_addr.addr_bytes[5] = 0 + iface_idx++;
> >> +		} else
> >> +			eth_random_addr((uint8_t *)&pmd->eth_addr);
> > 
> > To avoid checkpatch warning, use else { }.
> 
> Ferruh, states this is OK and does not need to have the { } added. I will not add the { } here.

Very well!

> 
> > 
> >> 	}
> >> 
> >> 	return 0;
> >> @@ -1285,6 +1304,16 @@ set_remote_iface(const char *key __rte_unused,
> >> 	return 0;
> >> }
> >> 
> >> +static int
> >> +set_mac_type(const char *key __rte_unused, const char *value, void *extra_args)
> >> +{
> >> +	/* Assume random mac address */
> >> +	*(int *)extra_args = 0;
> > 
> > With an automatic variable for fixed_mac_type in rte_pmd_tap_probe(), no need for setting it to 0 here.
> 
> It does need to be set of each instance of the call to this routine even if I remove the global. Each interface can have a different state.
> 
> > 
> >> +	if (value && !strcasecmp("fixed", value))
> > 
> > I think a macro for "fixed" would be better. Maybe a ETH_TAP_MAC_FIXED "fixed" at the top?
> 
> I will use the already existing macro ETH_TAP_MAC_ARG instead.
> > 
> >> +		*(int *)extra_args = 1;
> >> +	return 0;
> >> +}
> >> +
> >> /* Open a TAP interface device.
> >>  */
> >> static int
> >> @@ -1301,6 +1330,7 @@ rte_pmd_tap_probe(const char *name, const char *params)
> >> 		 DEFAULT_TAP_NAME, tap_unit++);
> >> 	memset(remote_iface, 0, RTE_ETH_NAME_MAX_LEN);
> >> 
> >> +	fixed_mac_type = 0;
> > 
> > Turn fixed_mac_type to an automatic variable, local to this function.
> > And add the argument to eth_dev_tap_create().
> 
> Need to have the global to exist, because I need to be able to test the variable later. The variable could be placed in a allocated structure, but does it really matter to have a static variable here?

I disagree here, I've seen fixed_mac_type only used during probing, in rte_pmd_tap_probe() and rte_eth_dev_tap_create().
The case is similar to the "iface" param, we need it during probing, where it is used appropriately (either setting the pmd->eth_addr for your fixed mac, or setting pmd->remote_iface for iface).

> 
> > 
> >> 	if (params && (params[0] != '\0')) {
> >> 		RTE_LOG(DEBUG, PMD, "paramaters (%s)\n", params);
> >> 
> >> @@ -1332,6 +1362,15 @@ rte_pmd_tap_probe(const char *name, const char *params)
> >> 				if (ret == -1)
> >> 					goto leave;
> >> 			}
> >> +
> >> +			if (rte_kvargs_count(kvlist, ETH_TAP_MAC_ARG) == 1) {
> >> +				ret = rte_kvargs_process(kvlist,
> >> +							 ETH_TAP_MAC_ARG,
> >> +							 &set_mac_type,
> >> +							 &fixed_mac_type);
> >> +				if (ret == -1)
> >> +					goto leave;
> >> +			}
> >> 		}
> >> 	}
> >> 	pmd_link.link_speed = speed;
> >> @@ -1394,4 +1433,8 @@ static struct rte_vdev_driver pmd_tap_drv = {
> >> };
> >> RTE_PMD_REGISTER_VDEV(net_tap, pmd_tap_drv);
> >> RTE_PMD_REGISTER_ALIAS(net_tap, eth_tap);
> >> -RTE_PMD_REGISTER_PARAM_STRING(net_tap, "iface=<string>,speed=N");
> >> +RTE_PMD_REGISTER_PARAM_STRING(net_tap,
> >> +			      "iface=<string>,"
> >> +			      "speed=N,"
> >> +			      "remote=<string>,"
> >> +			      "mac=fixed");
> > 
> > Indeed, I forgot to update that when I introduced the remote!
> > 
> > That's it for me,
> > Thank you.
> > 
> > Pascal
> 
> Regards,
> Keith
>