Index: sys/dev/pci/if_ixl.c
===================================================================
RCS file: /mount/openbsd/cvs/src/sys/dev/pci/if_ixl.c,v
diff -u -p -u -p -r1.102 if_ixl.c
--- sys/dev/pci/if_ixl.c	30 Oct 2024 18:02:45 -0000	1.102
+++ sys/dev/pci/if_ixl.c	3 Apr 2025 12:58:50 -0000
@@ -2949,6 +2949,14 @@ ixl_start(struct ifqueue *ifq)
 			continue;
 		}
 
+		if (ISSET(m->m_pkthdr.csum_flags, M_TCP_TSO)) {
+			struct ether_extracted ext;
+
+			ether_extract_headers(m, &ext);
+			KASSERT(m->m_pkthdr.len == ext.iplen + (ext.evh ?
+			    sizeof(*ext.evh) : sizeof(*ext.eh)));
+		}
+
 		bus_dmamap_sync(sc->sc_dmat, map, 0,
 		    map->dm_mapsize, BUS_DMASYNC_PREWRITE);