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SubjectRe: [PATCH v2] pktgen: create packet use IPv6 source address between src6_min and src6_max.
The subject line could use some rewording, I think.

On Mon, 13 Jan 2020 19:21:02 +0800, Niu Xilei wrote:
> Pktgen can use only one IPv6 source address from output device, or src6 command
> setting. In pressure test we need create lots of session more than 65536.If
> IPSRC_RND flag is set, generate random source address between src6_min and src6_max.
>
> Signed-off-by: Niu Xilei <niu_xilei@163.com>
>
> Changes since v1:
> - only create IPv6 source address over least significant 64 bit range

> +/* generate ipv6 source addr */
> +static inline void set_src_in6_addr(struct pktgen_dev *pkt_dev)

Please just use "static" instead of "static inline". The compiler will
be clever enough to decide the inlining.

> +{
> + __be64 min6_h, min6_l, max6_h, max6_l, addr_l, *t;
> + u64 min6, max6, rand, i;
> + struct in6_addr addr6;
> +
> + memcpy(&min6_h, pkt_dev->min_in6_saddr.s6_addr, 8);
> + memcpy(&min6_l, pkt_dev->min_in6_saddr.s6_addr + 8, 8);
> + memcpy(&max6_h, pkt_dev->max_in6_saddr.s6_addr, 8);
> + memcpy(&max6_l, pkt_dev->max_in6_saddr.s6_addr + 8, 8);
> +
> + /* only generate source address in least significant 64 bits range
> + * most significant 64 bits must be equal
> + */
> + if (max6_h != min6_h)
> + return;
> +
> + addr6 = pkt_dev->min_in6_saddr;
> + t = (__be64 *)addr6.s6_addr + 1;
> + min6 = be64_to_cpu(min6_l);
> + max6 = be64_to_cpu(max6_l);
> +
> + if (min6 < max6) {

Since this code is executed on every packet, would it be possible to
pre-compute the decision if the IPv6 address is to be generated or not?
We have 4 memcpy()s and 2 byte swaps, and the conditions never change,
so it could be computed at setup time, right?

> + if (pkt_dev->flags & F_IPSRC_RND) {
> + do {
> + prandom_bytes(&rand, sizeof(rand));
> + rand = rand % (max6 - min6) + min6;
> + addr_l = cpu_to_be64(rand);
> + memcpy(t, &addr_l, 8);
> + } while (ipv6_addr_loopback(&addr6) ||
> + ipv6_addr_v4mapped(&addr6) ||
> + ipv6_addr_is_multicast(&addr6));
> + } else {
> + addr6 = pkt_dev->cur_in6_saddr;
> + i = be64_to_cpu(*t);
> + if (++i > max6)
> + i = min6;
> + addr_l = cpu_to_be64(i);
> + memcpy(t, &addr_l, 8);
> + }
> + }
> + pkt_dev->cur_in6_saddr = addr6;
> +}

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