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, 18 insertions, 32 deletions

diff --git a/tcp.c b/tcp.c
index 5c40e18..2f900fc 100644
--- a/tcp.c
+++ b/tcp.c
@@ -909,21 +909,21 @@ static void tcp_fill_header(struct tcphdr *th,
  * @conn:		Connection pointer
  * @taph:		tap backend specific header
  * @iph:		Pointer to IPv4 header
- * @bp:			Pointer to TCP header followed by TCP payload
- * @dlen:		TCP payload length
+ * @th:			Pointer to TCP header
+ * @payload:		TCP payload
  * @check:		Checksum, if already known
  * @seq:		Sequence number for this segment
  * @no_tcp_csum:	Do not set TCP checksum
  */
 void tcp_fill_headers4(const struct tcp_tap_conn *conn,
 		       struct tap_hdr *taph, struct iphdr *iph,
-		       struct tcp_payload_t *bp, size_t dlen,
+		       struct tcphdr *th, struct iov_tail *payload,
 		       const uint16_t *check, uint32_t seq, bool no_tcp_csum)
 {
 	const struct flowside *tapside = TAPFLOW(conn);
 	const struct in_addr *src4 = inany_v4(&tapside->oaddr);
 	const struct in_addr *dst4 = inany_v4(&tapside->eaddr);
-	size_t l4len = dlen + sizeof(bp->th);
+	size_t l4len = iov_tail_size(payload) + sizeof(*th);
 	size_t l3len = l4len + sizeof(*iph);
 
 	ASSERT(src4 && dst4);
@@ -935,19 +935,12 @@ void tcp_fill_headers4(const struct tcp_tap_conn *conn,
 	iph->check = check ? *check :
 			     csum_ip4_header(l3len, IPPROTO_TCP, *src4, *dst4);
 
-	tcp_fill_header(&bp->th, conn, seq);
+	tcp_fill_header(th, conn, seq);
 
-	if (no_tcp_csum) {
-		bp->th.check = 0;
-	} else {
-		const struct iovec iov = {
-			.iov_base = bp->data,
-			.iov_len = dlen,
-		};
-		struct iov_tail payload = IOV_TAIL(&iov, 1, 0);
-
-		tcp_update_check_tcp4(iph, &bp->th, &payload);
-	}
+	if (no_tcp_csum)
+		th->check = 0;
+	else
+		tcp_update_check_tcp4(iph, th, payload);
 
 	tap_hdr_update(taph, l3len + sizeof(struct ethhdr));
 }
@@ -957,19 +950,19 @@ void tcp_fill_headers4(const struct tcp_tap_conn *conn,
  * @conn:		Connection pointer
  * @taph:		tap backend specific header
  * @ip6h:		Pointer to IPv6 header
- * @bp:			Pointer to TCP header followed by TCP payload
- * @dlen:		TCP payload length
+ * @th:			Pointer to TCP header
+ * @payload:		TCP payload
  * @check:		Checksum, if already known
  * @seq:		Sequence number for this segment
  * @no_tcp_csum:	Do not set TCP checksum
  */
 void tcp_fill_headers6(const struct tcp_tap_conn *conn,
 		       struct tap_hdr *taph, struct ipv6hdr *ip6h,
-		       struct tcp_payload_t *bp, size_t dlen,
+		       struct tcphdr *th, struct iov_tail *payload,
 		       uint32_t seq, bool no_tcp_csum)
 {
+	size_t l4len = iov_tail_size(payload) + sizeof(*th);
 	const struct flowside *tapside = TAPFLOW(conn);
-	size_t l4len = dlen + sizeof(bp->th);
 
 	ip6h->payload_len = htons(l4len);
 	ip6h->saddr = tapside->oaddr.a6;
@@ -983,19 +976,12 @@ void tcp_fill_headers6(const struct tcp_tap_conn *conn,
 	ip6h->flow_lbl[1] = (conn->sock >> 8) & 0xff;
 	ip6h->flow_lbl[2] = (conn->sock >> 0) & 0xff;
 
-	tcp_fill_header(&bp->th, conn, seq);
+	tcp_fill_header(th, conn, seq);
 
-	if (no_tcp_csum) {
-		bp->th.check = 0;
-	} else {
-		const struct iovec iov = {
-			.iov_base = bp->data,
-			.iov_len = dlen,
-		};
-		struct iov_tail payload = IOV_TAIL(&iov, 1, 0);
-
-		tcp_update_check_tcp6(ip6h, &bp->th, &payload);
-	}
+	if (no_tcp_csum)
+		th->check = 0;
+	else
+		tcp_update_check_tcp6(ip6h, th, payload);
 
 	tap_hdr_update(taph, l4len + sizeof(*ip6h) + sizeof(struct ethhdr));
 }