From: Stefan Sperling <stsp@stsp.name>
Subject: Re: SoftLRO: remove 8 segment limit
To: Jan Klemkow <jan@openbsd.org>
Cc: tech@openbsd.org
Date: Fri, 15 Aug 2025 14:00:37 +0200

On Thu, Aug 14, 2025 at 08:42:36PM +0200, Jan Klemkow wrote:
> Hi,
> 
> The limit of 8 segments is no longer needed after the last fix[1].
> Thus, this code can be removed.
> 
> ok?
> 
> bye,
> Jan

ok stsp@


> [1]: https://cvsweb.openbsd.org/src/sys/netinet/tcp_input.c?rev=1.458&content-type=text/x-cvsweb-markup
> 
> Index: netinet/tcp_input.c
> ===================================================================
> RCS file: /cvs/src/sys/netinet/tcp_input.c,v
> diff -u -p -r1.460 tcp_input.c
> --- netinet/tcp_input.c	14 Aug 2025 08:50:25 -0000	1.460
> +++ netinet/tcp_input.c	14 Aug 2025 18:33:59 -0000
> @@ -4500,8 +4500,7 @@ void
>  tcp_softlro_glue(struct mbuf_list *ml, struct mbuf *mtail, struct ifnet *ifp)
>  {
>  	struct ether_extracted head, tail;
> -	struct mbuf *m, *mhead;
> -	unsigned int headcnt, tailcnt;
> +	struct mbuf *mhead;
>  
>  	if (!ISSET(ifp->if_xflags, IFXF_LRO))
>  		goto dontmerge;
> @@ -4524,12 +4523,6 @@ tcp_softlro_glue(struct mbuf_list *ml, s
>  	if (!tcp_softlro_check(mtail, &tail))
>  		goto dontmerge;
>  
> -	tailcnt = 0;
> -	for (m = mtail; m != NULL; m = m->m_next) {
> -		if (tailcnt++ >= 8)
> -			goto dontmerge;
> -	}
> -
>  	mtail->m_pkthdr.ph_mss = tail.paylen;
>  
>  	for (mhead = ml->ml_head; mhead != NULL; mhead = mhead->m_nextpkt) {
> @@ -4563,13 +4556,6 @@ tcp_softlro_glue(struct mbuf_list *ml, s
>  		ether_extract_headers(mhead, &head);
>  		if (!tcp_softlro_compare(&head, &tail))
>  			continue;
> -
> -		/* Limit mbuf chain to avoid m_defrag calls when forwarding. */
> -		headcnt = tailcnt;
> -		for (m = mhead; m != NULL; m = m->m_next) {
> -			if (headcnt++ >= 8)
> -				goto dontmerge;
> -		}
>  
>  		tcp_softlro_concat(mhead, &head, mtail, &tail);
>  		return;
> 
>