Re: [PATCH] net/tap: add new macpair option for split MAC address

[Stephen Hemminger <stephen@networkplumber.org>]

On Tue, 17 Sep 2024 14:51:47 +0300
Isaac Boukris <iboukris@gmail.com> wrote:

> Normally, the MAC address of the kernel interface is the same as in the
> interface in dpdk, as they represent the same interface. It is useful
> to allow viewing them as separate connected interfaces (like ip's veth).
> 
> This solves a problem I have running a freebsd-based IPv6 stack on top
> of dpdk and using the tap interface, as both the kernel and freebsd
> stacks configure the MAC derived IPv6 address on the interface (as can
> be seen with ifconfig for the kernel), and they both complain about
> duplicate IPv6 address and the freebsd disables IPv6 as a result.
> 
> Signed-off-by: Isaac Boukris <iboukris@gmail.com>

Makes sense but a couple of small comments and rebase needed.

1. Could use rte_ether_addr_copy hear as is done elsewhere.
   And {} non needed.

@@ -2023,12 +2031,20 @@ eth_dev_tap_create(struct rte_vdev_device *vdev, const char *tap_name,
 	if (pmd->type == ETH_TUNTAP_TYPE_TAP) {
 		memset(&ifr, 0, sizeof(struct ifreq));
 		ifr.ifr_hwaddr.sa_family = AF_LOCAL;
-		rte_memcpy(ifr.ifr_hwaddr.sa_data, &pmd->eth_addr,
-				RTE_ETHER_ADDR_LEN);
+
+		if (mac_pair) {
+			rte_eth_random_addr((uint8_t *)ifr.ifr_hwaddr.sa_data);
+		} else {
+			memcpy(ifr.ifr_hwaddr.sa_data, &pmd->eth_addr,
+			       RTE_ETHER_ADDR_LEN);
		        rte_ether_addr_copy(&pmd->eth_addr, (struct rte_ether_addr *)&ifr.ifr_hwaddr.sa_data);

2. Need more error checks. macpair won't work with TUN device.
   and what happens if mac address is specified?
	

3. Should the mac address devarg, take two args?