From: Alexander Bluhm <bluhm@openbsd.org>
Subject: Re: vio(4): tso
To: Jan Klemkow <j.klemkow@wemelug.de>
Cc: Brian Conway <bconway@rcesoftware.com>, tech@openbsd.org
Date: Tue, 9 Apr 2024 22:23:00 +0200

On Tue, Apr 09, 2024 at 09:57:39PM +0200, Jan Klemkow wrote:
> ok?

OK bluhm@

> Index: dev/pv/if_vio.c
> ===================================================================
> RCS file: /cvs/src/sys/dev/pv/if_vio.c,v
> diff -u -p -r1.31 if_vio.c
> --- dev/pv/if_vio.c	14 Feb 2024 22:41:48 -0000	1.31
> +++ dev/pv/if_vio.c	9 Apr 2024 18:21:45 -0000
> @@ -43,12 +43,15 @@
>  
>  #include <net/if.h>
>  #include <net/if_media.h>
> +#include <net/route.h>
>  
>  #include <netinet/in.h>
>  #include <netinet/if_ether.h>
>  #include <netinet/ip.h>
>  #include <netinet/ip6.h>
>  #include <netinet/tcp.h>
> +#include <netinet/tcp_timer.h>
> +#include <netinet/tcp_var.h>
>  #include <netinet/udp.h>
>  
>  #if NBPFILTER > 0
> @@ -537,6 +540,9 @@ vio_attach(struct device *parent, struct
>  	    VIRTIO_NET_F_MRG_RXBUF | VIRTIO_NET_F_CSUM |
>  	    VIRTIO_F_RING_EVENT_IDX | VIRTIO_NET_F_GUEST_CSUM;
>  
> +	vsc->sc_driver_features |= VIRTIO_NET_F_HOST_TSO4;
> +	vsc->sc_driver_features |= VIRTIO_NET_F_HOST_TSO6;
> +
>  	virtio_negotiate_features(vsc, virtio_net_feature_names);
>  	if (virtio_has_feature(vsc, VIRTIO_NET_F_MAC)) {
>  		vio_get_lladdr(&sc->sc_ac, vsc);
> @@ -553,9 +559,9 @@ vio_attach(struct device *parent, struct
>  		sc->sc_hdr_size = offsetof(struct virtio_net_hdr, num_buffers);
>  	}
>  	if (virtio_has_feature(vsc, VIRTIO_NET_F_MRG_RXBUF))
> -		ifp->if_hardmtu = 16000; /* arbitrary limit */
> +		ifp->if_hardmtu = MAXMCLBYTES;
>  	else
> -		ifp->if_hardmtu = MCLBYTES - sc->sc_hdr_size - ETHER_HDR_LEN;
> +		ifp->if_hardmtu = MAXMCLBYTES - sc->sc_hdr_size - ETHER_HDR_LEN;
>  
>  	if (virtio_alloc_vq(vsc, &sc->sc_vq[VQRX], 0, MCLBYTES, 2, "rx") != 0)
>  		goto err;
> @@ -595,6 +601,10 @@ vio_attach(struct device *parent, struct
>  	if (virtio_has_feature(vsc, VIRTIO_NET_F_CSUM))
>  		ifp->if_capabilities |= IFCAP_CSUM_TCPv4|IFCAP_CSUM_UDPv4|
>  		    IFCAP_CSUM_TCPv6|IFCAP_CSUM_UDPv6;
> +	if (virtio_has_feature(vsc, VIRTIO_NET_F_HOST_TSO4))
> +		ifp->if_capabilities |= IFCAP_TSOv4;
> +	if (virtio_has_feature(vsc, VIRTIO_NET_F_HOST_TSO6))
> +		ifp->if_capabilities |= IFCAP_TSOv6;
>  	ifq_init_maxlen(&ifp->if_snd, vsc->sc_vqs[1].vq_num - 1);
>  	ifmedia_init(&sc->sc_media, 0, vio_media_change, vio_media_status);
>  	ifmedia_add(&sc->sc_media, IFM_ETHER | IFM_AUTO, 0, NULL);
> @@ -714,6 +724,85 @@ vio_stop(struct ifnet *ifp, int disable)
>  	}
>  }
>  
> +static inline uint16_t
> +vio_cksum_update(uint32_t cksum, uint16_t paylen)
> +{
> +	/* Add payload length */
> +	cksum += paylen;
> +
> +	/* Fold back to 16 bit */
> +	cksum += cksum >> 16;
> +
> +	return (uint16_t)(cksum);
> +}
> +
> +void
> +vio_tx_offload(struct virtio_net_hdr *hdr, struct mbuf *m)
> +{
> +	struct ether_extracted ext;
> +
> +	/*
> +	 * Checksum Offload
> +	 */
> +
> +	if (!ISSET(m->m_pkthdr.csum_flags, M_TCP_CSUM_OUT) &&
> +	    !ISSET(m->m_pkthdr.csum_flags, M_UDP_CSUM_OUT))
> +		return;
> +
> +	ether_extract_headers(m, &ext);
> +
> +	/* Consistency Checks */
> +	if ((!ext.ip4 && !ext.ip6) || (!ext.tcp && !ext.udp))
> +		return;
> +
> +	if ((ext.tcp && !ISSET(m->m_pkthdr.csum_flags, M_TCP_CSUM_OUT)) ||
> +	    (ext.udp && !ISSET(m->m_pkthdr.csum_flags, M_UDP_CSUM_OUT)))
> +		return;
> +
> +	hdr->csum_start = sizeof(*ext.eh);
> +#if NVLAN > 0
> +	if (ext.evh)
> +		hdr->csum_start = sizeof(*ext.evh);
> +#endif
> +	hdr->csum_start += ext.iphlen;
> +
> +	if (ext.tcp)
> +		hdr->csum_offset = offsetof(struct tcphdr, th_sum);
> +	else if (ext.udp)
> +		hdr->csum_offset = offsetof(struct udphdr, uh_sum);
> +
> +	hdr->flags = VIRTIO_NET_HDR_F_NEEDS_CSUM;
> +
> +	/*
> +	 * TCP Segmentation Offload
> +	 */
> +
> +	if (!ISSET(m->m_pkthdr.csum_flags, M_TCP_TSO))
> +		return;
> +
> +	if (!ext.tcp) {
> +		tcpstat_inc(tcps_outbadtso);
> +		return;
> +	}
> +
> +	hdr->hdr_len = hdr->csum_start + ext.tcphlen;
> +	hdr->gso_size = m->m_pkthdr.ph_mss;
> +
> +	if (ext.ip4)
> +		hdr->gso_type = VIRTIO_NET_HDR_GSO_TCPV4;
> +#ifdef INET6
> +	else if (ext.ip6)
> +		hdr->gso_type = VIRTIO_NET_HDR_GSO_TCPV6;
> +#endif
> +
> +	/* VirtIO-Net need pseudo header cksum with IP-payload length for TSO */
> +	ext.tcp->th_sum = vio_cksum_update(ext.tcp->th_sum,
> +	    htons(ext.iplen - ext.iphlen));
> +
> +	tcpstat_add(tcps_outpkttso,
> +	    (ext.paylen + m->m_pkthdr.ph_mss - 1) / m->m_pkthdr.ph_mss);
> +}
> +
>  void
>  vio_start(struct ifnet *ifp)
>  {
> @@ -750,24 +839,7 @@ again:
>  
>  		hdr = &sc->sc_tx_hdrs[slot];
>  		memset(hdr, 0, sc->sc_hdr_size);
> -		if (m->m_pkthdr.csum_flags & (M_TCP_CSUM_OUT|M_UDP_CSUM_OUT)) {
> -			struct ether_extracted ext;
> -
> -			ether_extract_headers(m, &ext);
> -			hdr->csum_start = sizeof(*ext.eh);
> -#if NVLAN > 0
> -			if (ext.evh)
> -				hdr->csum_start = sizeof(*ext.evh);
> -#endif
> -			if (m->m_pkthdr.csum_flags & M_TCP_CSUM_OUT)
> -				hdr->csum_offset = offsetof(struct tcphdr, th_sum);
> -			else
> -				hdr->csum_offset = offsetof(struct udphdr, uh_sum);
> -
> -			if (ext.ip4 || ext.ip6)
> -				hdr->csum_start += ext.iphlen;
> -			hdr->flags = VIRTIO_NET_HDR_F_NEEDS_CSUM;
> -		}
> +		vio_tx_offload(hdr, m);
>  
>  		r = vio_encap(sc, slot, m);
>  		if (r != 0) {