[PATCH 09/10] tcp: Pass explicit data length to tcp_fill_headers()

[Laurent Vivier <lvivier@redhat.com>]

tcp_fill_headers() computed the TCP payload length from iov_tail_size(),
but with vhost-user multibuffer frames, the iov_tail will be larger than
the actual data.  Pass the data length explicitly so that IP total
length, pseudo-header, and checksum computations use the correct value.

Signed-off-by: Laurent Vivier <lvivier@redhat.com>
---
 tcp.c          | 5 +++--
 tcp_buf.c      | 3 ++-
 tcp_internal.h | 2 +-
 tcp_vu.c       | 9 +++++----
 4 files changed, 11 insertions(+), 8 deletions(-)

diff --git a/tcp.c b/tcp.c
index 49c6fb57ce16..6b0e25f33bf1 100644
--- a/tcp.c
+++ b/tcp.c
@@ -945,6 +945,7 @@ static void tcp_fill_header(struct tcphdr *th,
  * @ip6h:		Pointer to IPv6 header, or NULL
  * @th:			Pointer to TCP header
  * @payload:		TCP payload
+ * @dlen:		TCP payload length
  * @ip4_check:		IPv4 checksum, if already known
  * @seq:		Sequence number for this segment
  * @no_tcp_csum:	Do not set TCP checksum
@@ -955,11 +956,11 @@ size_t tcp_fill_headers(const struct ctx *c, struct tcp_tap_conn *conn,
 			struct ethhdr *eh,
 			struct iphdr *ip4h, struct ipv6hdr *ip6h,
 			struct tcphdr *th, struct iov_tail *payload,
-			const uint16_t *ip4_check, uint32_t seq,
+			size_t dlen, const uint16_t *ip4_check, uint32_t seq,
 			bool no_tcp_csum)
 {
 	const struct flowside *tapside = TAPFLOW(conn);
-	size_t l4len = iov_tail_size(payload) + sizeof(*th);
+	size_t l4len = dlen + sizeof(*th);
 	uint8_t *omac = conn->f.tap_omac;
 	size_t l3len = l4len;
 	uint32_t psum = 0;
diff --git a/tcp_buf.c b/tcp_buf.c
index 41965b107567..27151854033c 100644
--- a/tcp_buf.c
+++ b/tcp_buf.c
@@ -190,7 +190,8 @@ static void tcp_l2_buf_fill_headers(const struct ctx *c,
 	else
 		ip6h = iov[TCP_IOV_IP].iov_base;
 
-	l2len = tcp_fill_headers(c, conn, eh, ip4h, ip6h, th, &tail, check, seq,
+	l2len = tcp_fill_headers(c, conn, eh, ip4h, ip6h, th, &tail,
+				 iov_tail_size(&tail), check, seq,
 				 no_tcp_csum);
 	tap_hdr_update(taph, l2len);
 }
diff --git a/tcp_internal.h b/tcp_internal.h
index d9408852571f..a0fa19f4ed11 100644
--- a/tcp_internal.h
+++ b/tcp_internal.h
@@ -187,7 +187,7 @@ size_t tcp_fill_headers(const struct ctx *c, struct tcp_tap_conn *conn,
 			struct ethhdr *eh,
 			struct iphdr *ip4h, struct ipv6hdr *ip6h,
 			struct tcphdr *th, struct iov_tail *payload,
-			const uint16_t *ip4_check, uint32_t seq,
+			size_t dlen, const uint16_t *ip4_check, uint32_t seq,
 			bool no_tcp_csum);
 
 int tcp_update_seqack_wnd(const struct ctx *c, struct tcp_tap_conn *conn,
diff --git a/tcp_vu.c b/tcp_vu.c
index 105bca41c6de..ae79a6d856b0 100644
--- a/tcp_vu.c
+++ b/tcp_vu.c
@@ -135,7 +135,7 @@ int tcp_vu_send_flag(const struct ctx *c, struct tcp_tap_conn *conn, int flags)
 		seq--;
 
 	tcp_fill_headers(c, conn, eh, ip4h, ip6h, th, &payload,
-			 NULL, seq, !*c->pcap);
+			 optlen, NULL, seq, !*c->pcap);
 
 	l2len = optlen + hdrlen - VNET_HLEN;
 	vu_pad(&flags_elem[0].in_sg[0], l2len);
@@ -280,12 +280,13 @@ static ssize_t tcp_vu_sock_recv(const struct ctx *c, struct vu_virtq *vq,
  * @conn:		Connection pointer
  * @iov:		Pointer to the array of IO vectors
  * @iov_cnt:		Number of entries in @iov
+ * @dlen:		Data length
  * @check:		Checksum, if already known
  * @no_tcp_csum:	Do not set TCP checksum
  * @push:		Set PSH flag, last segment in a batch
  */
 static void tcp_vu_prepare(const struct ctx *c, struct tcp_tap_conn *conn,
-			   struct iovec *iov, size_t iov_cnt,
+			   struct iovec *iov, size_t iov_cnt, size_t dlen,
 			   const uint16_t **check, bool no_tcp_csum, bool push)
 {
 	const struct flowside *toside = TAPFLOW(conn);
@@ -329,7 +330,7 @@ static void tcp_vu_prepare(const struct ctx *c, struct tcp_tap_conn *conn,
 	th->ack = 1;
 	th->psh = push;
 
-	tcp_fill_headers(c, conn, eh, ip4h, ip6h, th, &payload,
+	tcp_fill_headers(c, conn, eh, ip4h, ip6h, th, &payload, dlen,
 			 *check, conn->seq_to_tap, no_tcp_csum);
 	if (ip4h)
 		*check = &ip4h->check;
@@ -457,7 +458,7 @@ int tcp_vu_data_from_sock(const struct ctx *c, struct tcp_tap_conn *conn)
 			check = NULL;
 		previous_dlen = dlen;
 
-		tcp_vu_prepare(c, conn, iov, buf_cnt, &check, !*c->pcap, push);
+		tcp_vu_prepare(c, conn, iov, buf_cnt, dlen, &check, !*c->pcap, push);
 
 		/* Pad first/single buffer only, it's at least ETH_ZLEN long */
 		l2len = dlen + hdrlen - VNET_HLEN;
-- 
2.53.0