git: 41988a137d55 - stable/13 - if_tuntap: support receive checksum offloading for tap interfaces

The branch stable/13 has been updated by tuexen:

URL: https://cgit.FreeBSD.org/src/commit/?id=41988a137d556b0e4bd6259bc7af0c63f6975596

commit 41988a137d556b0e4bd6259bc7af0c63f6975596
Author:     Michael Tuexen <tuexen@FreeBSD.org>
AuthorDate: 2023-11-09 10:37:27 +0000
Commit:     Michael Tuexen <tuexen@FreeBSD.org>
CommitDate: 2024-01-12 17:53:19 +0000

    if_tuntap: support receive checksum offloading for tap interfaces
    
    When enabled, pretend that the IPv4 and transport layer checksum
    is correct for packets injected via the character device.
    This is a prerequisite for adding support for LRO, which will
    be added next. Then packetdrill can be used to test the LRO
    code in local mode.
    
    Reviewed by:            rscheff, zlei
    Sponsored by:           Netflix, Inc.
    Differential Revision:  https://reviews.freebsd.org/D42477
    
    (cherry picked from commit ff69d13a50d1d07601de0885fd94f6a09a7ba383)
---
 sys/net/if_tuntap.c | 34 +++++++++++++++++++++++++++++++---
 1 file changed, 31 insertions(+), 3 deletions(-)

diff --git a/sys/net/if_tuntap.c b/sys/net/if_tuntap.c
index 29e9c05e52bc..9cadd971eb37 100644
--- a/sys/net/if_tuntap.c
+++ b/sys/net/if_tuntap.c
@@ -970,6 +970,8 @@ tuncreate(struct cdev *dev)
 	ifp->if_flags = iflags;
 	IFQ_SET_MAXLEN(&ifp->if_snd, ifqmaxlen);
 	ifp->if_capabilities |= IFCAP_LINKSTATE;
+	if ((tp->tun_flags & TUN_L2) != 0)
+		ifp->if_capabilities |= IFCAP_RXCSUM | IFCAP_RXCSUM_IPV6;
 	ifp->if_capenable |= IFCAP_LINKSTATE;
 
 	if ((tp->tun_flags & TUN_L2) != 0) {
@@ -1777,9 +1779,35 @@ tunwrite_l2(struct tuntap_softc *tp, struct mbuf *m,
 		return (0);
 	}
 
-	if (vhdr != NULL && virtio_net_rx_csum(m, &vhdr->hdr)) {
-		m_freem(m);
-		return (0);
+	if (vhdr != NULL) {
+		if (virtio_net_rx_csum(m, &vhdr->hdr)) {
+			m_freem(m);
+			return (0);
+		}
+	} else {
+		switch (ntohs(eh->ether_type)) {
+#ifdef INET
+		case ETHERTYPE_IP:
+			if (ifp->if_capenable & IFCAP_RXCSUM) {
+				m->m_pkthdr.csum_flags |=
+				    CSUM_IP_CHECKED | CSUM_IP_VALID |
+				    CSUM_DATA_VALID | CSUM_SCTP_VALID |
+				    CSUM_PSEUDO_HDR;
+				m->m_pkthdr.csum_data = 0xffff;
+			}
+			break;
+#endif
+#ifdef INET6
+		case ETHERTYPE_IPV6:
+			if (ifp->if_capenable & IFCAP_RXCSUM_IPV6) {
+				m->m_pkthdr.csum_flags |=
+				    CSUM_DATA_VALID_IPV6 | CSUM_SCTP_VALID |
+				    CSUM_PSEUDO_HDR;
+				m->m_pkthdr.csum_data = 0xffff;
+			}
+			break;
+#endif
+		}
 	}
 
 	/* Pass packet up to parent. */