TSO engine of L1 requires a separate DMA descriptor for TCP

payload.  This means driver has to split a TX buffer into two
pieces of TX buffers when the TX buffer contains both
ethernet/IP/TCP header and partial TCP payload.  The controller
does not require all header should be in a TX buffer but driver
forced it to compute IP/TCP header size/offset which is required
parameter to configure DMA descriptor for TSO.
While here, slightly reorder DMA descriptor setup to enhance
readability and remove unnecessary code for TSO(upper stack never
requests TSO when the frame length is less than or equal to MTU).

Reported by:	Yamagi Burmeister <lists <> yamagi dot org>
Tested by:	Yamagi Burmeister <lists <> yamagi dot org>
MFC After:	1 week

1 files changed, 49 insertions, 32 deletions

diff --git a/sys/dev/age/if_age.c b/sys/dev/age/if_age.c
index 175dd9764787..7bc56a75da0c 100644
--- a/sys/dev/age/if_age.c
+++ b/sys/dev/age/if_age.c
@@ -1495,7 +1495,7 @@ age_encap(struct age_softc *sc, struct mbuf **m_head)
 	struct tcphdr *tcp;
 	bus_dma_segment_t txsegs[AGE_MAXTXSEGS];
 	bus_dmamap_t map;
-	uint32_t cflags, ip_off, poff, vtag;
+	uint32_t cflags, hdrlen, ip_off, poff, vtag;
 	int error, i, nsegs, prod, si;
 
 	AGE_LOCK_ASSERT(sc);
@@ -1562,8 +1562,12 @@ age_encap(struct age_softc *sc, struct mbuf **m_head)
 				*m_head = NULL;
 				return (ENOBUFS);
 			}
-			ip = (struct ip *)(mtod(m, char *) + ip_off);
 			tcp = (struct tcphdr *)(mtod(m, char *) + poff);
+			m = m_pullup(m, poff + (tcp->th_off << 2));
+			if (m == NULL) {
+				*m_head = NULL;
+				return (ENOBUFS);
+			}
 			/*
 			 * L1 requires IP/TCP header size and offset as
 			 * well as TCP pseudo checksum which complicates
@@ -1578,14 +1582,11 @@ age_encap(struct age_softc *sc, struct mbuf **m_head)
 			 * Reset IP checksum and recompute TCP pseudo
 			 * checksum as NDIS specification said.
 			 */
+			ip = (struct ip *)(mtod(m, char *) + ip_off);
+			tcp = (struct tcphdr *)(mtod(m, char *) + poff);
 			ip->ip_sum = 0;
-			if (poff + (tcp->th_off << 2) == m->m_pkthdr.len)
-				tcp->th_sum = in_pseudo(ip->ip_src.s_addr,
-				    ip->ip_dst.s_addr,
-				    htons((tcp->th_off << 2) + IPPROTO_TCP));
-			else
-				tcp->th_sum = in_pseudo(ip->ip_src.s_addr,
-				    ip->ip_dst.s_addr, htons(IPPROTO_TCP));
+			tcp->th_sum = in_pseudo(ip->ip_src.s_addr,
+			    ip->ip_dst.s_addr, htons(IPPROTO_TCP));
 		}
 		*m_head = m;
 	}
@@ -1627,23 +1628,48 @@ age_encap(struct age_softc *sc, struct mbuf **m_head)
 	}
 
 	m = *m_head;
+	/* Configure VLAN hardware tag insertion. */
+	if ((m->m_flags & M_VLANTAG) != 0) {
+		vtag = AGE_TX_VLAN_TAG(m->m_pkthdr.ether_vtag);
+		vtag = ((vtag << AGE_TD_VLAN_SHIFT) & AGE_TD_VLAN_MASK);
+		cflags |= AGE_TD_INSERT_VLAN_TAG;
+	}
+
+	desc = NULL;
+	i = 0;
 	if ((m->m_pkthdr.csum_flags & CSUM_TSO) != 0) {
-		/* Configure TSO. */
-		if (poff + (tcp->th_off << 2) == m->m_pkthdr.len) {
-			/* Not TSO but IP/TCP checksum offload. */
-			cflags |= AGE_TD_IPCSUM | AGE_TD_TCPCSUM;
-			/* Clear TSO in order not to set AGE_TD_TSO_HDR. */
-			m->m_pkthdr.csum_flags &= ~CSUM_TSO;
-		} else {
-			/* Request TSO and set MSS. */
-			cflags |= AGE_TD_TSO_IPV4;
-			cflags |= AGE_TD_IPCSUM | AGE_TD_TCPCSUM;
-			cflags |= ((uint32_t)m->m_pkthdr.tso_segsz <<
-			    AGE_TD_TSO_MSS_SHIFT);
-		}
+		/* Request TSO and set MSS. */
+		cflags |= AGE_TD_TSO_IPV4;
+		cflags |= AGE_TD_IPCSUM | AGE_TD_TCPCSUM;
+		cflags |= ((uint32_t)m->m_pkthdr.tso_segsz <<
+		    AGE_TD_TSO_MSS_SHIFT);
 		/* Set IP/TCP header size. */
 		cflags |= ip->ip_hl << AGE_TD_IPHDR_LEN_SHIFT;
 		cflags |= tcp->th_off << AGE_TD_TSO_TCPHDR_LEN_SHIFT;
+		/*
+		 * L1 requires the first buffer should only hold IP/TCP
+		 * header data. TCP payload should be handled in other
+		 * descriptors.
+		 */
+		hdrlen = poff + (tcp->th_off << 2);
+		desc = &sc->age_rdata.age_tx_ring[prod];
+		desc->addr = htole64(txsegs[0].ds_addr);
+		desc->len = htole32(AGE_TX_BYTES(hdrlen) | vtag);
+		desc->flags = htole32(cflags);
+		sc->age_cdata.age_tx_cnt++;
+		AGE_DESC_INC(prod, AGE_TX_RING_CNT);
+		if (m->m_len - hdrlen > 0) {
+			/* Handle remaining payload of the 1st fragment. */
+			desc = &sc->age_rdata.age_tx_ring[prod];
+			desc->addr = htole64(txsegs[0].ds_addr + hdrlen);
+			desc->len = htole32(AGE_TX_BYTES(m->m_len - hdrlen) |
+			    vtag);
+			desc->flags = htole32(cflags);
+			sc->age_cdata.age_tx_cnt++;
+			AGE_DESC_INC(prod, AGE_TX_RING_CNT);
+		}
+		/* Handle remaining fragments. */
+		i = 1;
 	} else if ((m->m_pkthdr.csum_flags & AGE_CSUM_FEATURES) != 0) {
 		/* Configure Tx IP/TCP/UDP checksum offload. */
 		cflags |= AGE_TD_CSUM;
@@ -1657,16 +1683,7 @@ age_encap(struct age_softc *sc, struct mbuf **m_head)
 		cflags |= ((poff + m->m_pkthdr.csum_data) <<
 		    AGE_TD_CSUM_XSUMOFFSET_SHIFT);
 	}
-
-	/* Configure VLAN hardware tag insertion. */
-	if ((m->m_flags & M_VLANTAG) != 0) {
-		vtag = AGE_TX_VLAN_TAG(m->m_pkthdr.ether_vtag);
-		vtag = ((vtag << AGE_TD_VLAN_SHIFT) & AGE_TD_VLAN_MASK);
-		cflags |= AGE_TD_INSERT_VLAN_TAG;
-	}
-
-	desc = NULL;
-	for (i = 0; i < nsegs; i++) {
+	for (; i < nsegs; i++) {
 		desc = &sc->age_rdata.age_tx_ring[prod];
 		desc->addr = htole64(txsegs[i].ds_addr);
 		desc->len = htole32(AGE_TX_BYTES(txsegs[i].ds_len) | vtag);