Re: [PATCH net 2/2] ipv4: reserve one IP ID per segment for UDP GSO packets

[David Ahern <dsahern@kernel.org>]

On 9/29/26 8:12 AM, Eric Dumazet wrote:
> @@ -1464,7 +1465,19 @@ struct sk_buff *__ip_make_skb(struct sock *sk,
>  	iph->ttl = ttl;
>  	iph->protocol = sk->sk_protocol;
>  	ip_copy_addrs(iph, fl4);
> -	ip_select_ident(net, skb, sk);
> +
> +	/* UDP GSO packets are segmented later (see udp_send_skb()):
> +	 * reserve one IP ID per segment.
> +	 */
> +	segs = 1;
> +	if (cork->gso_size) {
> +		int datalen = skb->len - skb_transport_offset(skb) -
> +			      sizeof(struct udphdr);

hard coding a specific transport header in L3 code is crossing layers.


> +
> +		if (datalen > cork->gso_size)
> +			segs = DIV_ROUND_UP(datalen, cork->gso_size);
> +	}
> +	ip_select_ident_segs(net, skb, sk, segs);
>  
>  	if (opt) {
>  		iph->ihl += opt->optlen >> 2;