tcp: Pass TCP header and payload separately to tcp_fill_headers[46]()

At the moment these take separate pointers to the tap specific and IP
headers, but expect the TCP header and payload as a single tcp_payload_t.
As well as being slightly inconsistent, this involves some slightly iffy
pointer shenanigans when called on the flags path with a tcp_flags_t
instead of a tcp_payload_t.

More importantly, it's inconvenient for the upcoming vhost-user case, where
the TCP header and payload might not be contiguous.  Furthermore, the
payload itself might not be contiguous.

So, pass the TCP header as its own pointer, and the TCP payload as an IO
vector.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

1 files changed, 35 insertions, 28 deletions

diff --git a/tcp_vu.c b/tcp_vu.c
index 134650e..470649e 100644
--- a/tcp_vu.c
+++ b/tcp_vu.c
@@ -104,10 +104,12 @@ int tcp_vu_send_flag(const struct ctx *c, struct tcp_tap_conn *conn, int flags)
 	const struct flowside *tapside = TAPFLOW(conn);
 	size_t optlen, hdrlen;
 	struct vu_virtq_element flags_elem[2];
-	struct tcp_payload_t *payload;
 	struct ipv6hdr *ip6h = NULL;
 	struct iovec flags_iov[2];
+	struct tcp_syn_opts *opts;
 	struct iphdr *iph = NULL;
+	struct iov_tail payload;
+	struct tcphdr *th;
 	struct ethhdr *eh;
 	uint32_t seq;
 	int elem_cnt;
@@ -139,35 +141,35 @@ int tcp_vu_send_flag(const struct ctx *c, struct tcp_tap_conn *conn, int flags)
 		iph = vu_ip(flags_elem[0].in_sg[0].iov_base);
 		*iph = (struct iphdr)L2_BUF_IP4_INIT(IPPROTO_TCP);
 
-		payload = vu_payloadv4(flags_elem[0].in_sg[0].iov_base);
+		th = vu_payloadv4(flags_elem[0].in_sg[0].iov_base);
 	} else {
 		eh->h_proto = htons(ETH_P_IPV6);
 
 		ip6h = vu_ip(flags_elem[0].in_sg[0].iov_base);
 		*ip6h = (struct ipv6hdr)L2_BUF_IP6_INIT(IPPROTO_TCP);
-		payload = vu_payloadv6(flags_elem[0].in_sg[0].iov_base);
+		th = vu_payloadv6(flags_elem[0].in_sg[0].iov_base);
 	}
 
-	memset(&payload->th, 0, sizeof(payload->th));
-	payload->th.doff = offsetof(struct tcp_payload_t, data) / 4;
-	payload->th.ack = 1;
+	memset(th, 0, sizeof(*th));
+	th->doff = sizeof(*th) / 4;
+	th->ack = 1;
 
 	seq = conn->seq_to_tap;
-	ret = tcp_prepare_flags(c, conn, flags, &payload->th,
-				(struct tcp_syn_opts *)payload->data,
-				&optlen);
+	opts = (struct tcp_syn_opts *)(th + 1);
+	ret = tcp_prepare_flags(c, conn, flags, th, opts, &optlen);
 	if (ret <= 0) {
 		vu_queue_rewind(vq, 1);
 		return ret;
 	}
 
 	flags_elem[0].in_sg[0].iov_len = hdrlen + optlen;
+	payload = IOV_TAIL(flags_elem[0].in_sg, 1, hdrlen);
 
 	if (CONN_V4(conn)) {
-		tcp_fill_headers4(conn, NULL, iph, payload, optlen, NULL, seq,
-				  true);
+		tcp_fill_headers4(conn, NULL, iph, th, &payload,
+				  NULL, seq, true);
 	} else {
-		tcp_fill_headers6(conn, NULL, ip6h, payload, optlen, seq, true);
+		tcp_fill_headers6(conn, NULL, ip6h, th, &payload, seq, true);
 	}
 
 	if (*c->pcap) {
@@ -317,23 +319,28 @@ static ssize_t tcp_vu_sock_recv(const struct ctx *c,
  * tcp_vu_prepare() - Prepare the frame header
  * @c:		Execution context
  * @conn:	Connection pointer
- * @first:	Pointer to the array of IO vectors
- * @dlen:	Packet data length
+ * @iov:	Pointer to the array of IO vectors
+ * @iov_cnt:	Number of entries in @iov
  * @check:	Checksum, if already known
  */
-static void tcp_vu_prepare(const struct ctx *c,
-			   struct tcp_tap_conn *conn, char *base,
-			   size_t dlen, const uint16_t **check)
+static void tcp_vu_prepare(const struct ctx *c, struct tcp_tap_conn *conn,
+			   struct iovec *iov, size_t iov_cnt,
+			   const uint16_t **check)
 {
 	const struct flowside *toside = TAPFLOW(conn);
-	struct tcp_payload_t *payload;
+	bool v6 = !(inany_v4(&toside->eaddr) && inany_v4(&toside->oaddr));
+	size_t hdrlen = tcp_vu_hdrlen(v6);
+	struct iov_tail payload = IOV_TAIL(iov, iov_cnt, hdrlen);
+	char *base = iov[0].iov_base;
 	struct ipv6hdr *ip6h = NULL;
 	struct iphdr *iph = NULL;
+	struct tcphdr *th;
 	struct ethhdr *eh;
 
 	/* we guess the first iovec provided by the guest can embed
 	 * all the headers needed by L2 frame
 	 */
+	ASSERT(iov[0].iov_len >= hdrlen);
 
 	eh = vu_eth(base);
 
@@ -342,31 +349,31 @@ static void tcp_vu_prepare(const struct ctx *c,
 
 	/* initialize header */
 
-	if (inany_v4(&toside->eaddr) && inany_v4(&toside->oaddr)) {
+	if (!v6) {
 		eh->h_proto = htons(ETH_P_IP);
 
 		iph = vu_ip(base);
 		*iph = (struct iphdr)L2_BUF_IP4_INIT(IPPROTO_TCP);
-		payload = vu_payloadv4(base);
+		th = vu_payloadv4(base);
 	} else {
 		eh->h_proto = htons(ETH_P_IPV6);
 
 		ip6h = vu_ip(base);
 		*ip6h = (struct ipv6hdr)L2_BUF_IP6_INIT(IPPROTO_TCP);
 
-		payload = vu_payloadv6(base);
+		th = vu_payloadv6(base);
 	}
 
-	memset(&payload->th, 0, sizeof(payload->th));
-	payload->th.doff = offsetof(struct tcp_payload_t, data) / 4;
-	payload->th.ack = 1;
+	memset(th, 0, sizeof(*th));
+	th->doff = sizeof(*th) / 4;
+	th->ack = 1;
 
-	if (inany_v4(&toside->eaddr) && inany_v4(&toside->oaddr)) {
-		tcp_fill_headers4(conn, NULL, iph, payload, dlen,
+	if (!v6) {
+		tcp_fill_headers4(conn, NULL, iph, th, &payload,
 				  *check, conn->seq_to_tap, true);
 		*check = &iph->check;
 	} else {
-		tcp_fill_headers6(conn, NULL, ip6h, payload, dlen,
+		tcp_fill_headers6(conn, NULL, ip6h, th, &payload,
 				  conn->seq_to_tap, true);
 	}
 }
@@ -478,7 +485,7 @@ int tcp_vu_data_from_sock(const struct ctx *c, struct tcp_tap_conn *conn)
 		if (i + 1 == head_cnt)
 			check = NULL;
 
-		tcp_vu_prepare(c, conn, iov->iov_base, dlen, &check);
+		tcp_vu_prepare(c, conn, iov, buf_cnt, &check);
 
 		if (*c->pcap) {
 			tcp_vu_update_check(tapside, iov, buf_cnt);