[PATCH] tcp: Use tcp_payload_t rather than tcphdr - dev

20 Sep 2024

As tcp_update_check_tcp4() and tcp_update_check_tcp6() compute the
checksum using the TCP header and the TCP payload, it is clearer
to use a pointer to tcp_payload_t that includes tcphdr and payload
rather than a pointer to tcphdr (and guessing TCP header is
followed by the payload).

Move tcp_payload_t and tcp_flags_t to tcp_internal.h.
(They will be used also by vhost-user).

Signed-off-by: Laurent Vivier &lt;lvivier(a)redhat.com&gt;
---
 tcp.c          | 42 ++++++++++++++++++++++--------------------
 tcp_buf.c      | 29 -----------------------------
 tcp_internal.h | 29 +++++++++++++++++++++++++++++
 3 files changed, 51 insertions(+), 49 deletions(-)

diff --git a/tcp.c b/tcp.c
index 1962fcc469ed..c9472d905520 100644
--- a/tcp.c
+++ b/tcp.c
@@ -757,32 +757,34 @@ static void tcp_sock_set_bufsize(const struct ctx *c, int s)
 /**
  * tcp_update_check_tcp4() - Update TCP checksum from stored one
  * @iph:	IPv4 header
- * @th:		TCP header followed by TCP payload
+ * @bp:		TCP header followed by TCP payload
  */
-static void tcp_update_check_tcp4(const struct iphdr *iph, struct tcphdr *th)
+static void tcp_update_check_tcp4(const struct iphdr *iph,
+				  struct tcp_payload_t *bp)
 {
 	uint16_t l4len = ntohs(iph->tot_len) - sizeof(struct iphdr);
 	struct in_addr saddr = { .s_addr = iph->saddr };
 	struct in_addr daddr = { .s_addr = iph->daddr };
 	uint32_t sum = proto_ipv4_header_psum(l4len, IPPROTO_TCP, saddr, daddr);
 
-	th->check = 0;
-	th->check = csum(th, l4len, sum);
+	bp->th.check = 0;
+	bp->th.check = csum(bp, l4len, sum);
 }
 
 /**
  * tcp_update_check_tcp6() - Calculate TCP checksum for IPv6
  * @ip6h:	IPv6 header
- * @th:		TCP header followed by TCP payload
+ * @bp:		TCP header followed by TCP payload
  */
-static void tcp_update_check_tcp6(struct ipv6hdr *ip6h, struct tcphdr *th)
+static void tcp_update_check_tcp6(const struct ipv6hdr *ip6h,
+				  struct tcp_payload_t *bp)
 {
 	uint16_t l4len = ntohs(ip6h->payload_len);
 	uint32_t sum = proto_ipv6_header_psum(l4len, IPPROTO_TCP,
 					      &ip6h->saddr, &ip6h->daddr);
 
-	th->check = 0;
-	th->check = csum(th, l4len, sum);
+	bp->th.check = 0;
+	bp->th.check = csum(bp, l4len, sum);
 }
 
 /**
@@ -902,7 +904,7 @@ static void tcp_fill_header(struct tcphdr *th,
  * @conn:		Connection pointer
  * @taph:		tap backend specific header
  * @iph:		Pointer to IPv4 header
- * @th:			Pointer to TCP header
+ * @bp:			Pointer to TCP header followed by TCP payload
  * @dlen:		TCP payload length
  * @check:		Checksum, if already known
  * @seq:		Sequence number for this segment
@@ -912,14 +914,14 @@ static void tcp_fill_header(struct tcphdr *th,
  */
 static size_t tcp_fill_headers4(const struct tcp_tap_conn *conn,
 				struct tap_hdr *taph,
-				struct iphdr *iph, struct tcphdr *th,
+				struct iphdr *iph, struct tcp_payload_t *bp,
 				size_t dlen, 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(*th);
+	size_t l4len = dlen + sizeof(bp->th);
 	size_t l3len = l4len + sizeof(*iph);
 
 	ASSERT(src4 && dst4);
@@ -931,12 +933,12 @@ static size_t tcp_fill_headers4(const struct tcp_tap_conn *conn,
 	iph->check = check ? *check :
 			     csum_ip4_header(l3len, IPPROTO_TCP, *src4, *dst4);
 
-	tcp_fill_header(th, conn, seq);
+	tcp_fill_header(&bp->th, conn, seq);
 
 	if (no_tcp_csum)
-		th->check = 0;
+		bp->th.check = 0;
 	else
-		tcp_update_check_tcp4(iph, th);
+		tcp_update_check_tcp4(iph, bp);
 
 	tap_hdr_update(taph, l3len + sizeof(struct ethhdr));
 
@@ -948,7 +950,7 @@ static size_t tcp_fill_headers4(const struct tcp_tap_conn *conn,
  * @conn:		Connection pointer
  * @taph:		tap backend specific header
  * @ip6h:		Pointer to IPv6 header
- * @th:			Pointer to TCP header
+ * @bp:			Pointer to TCP header followed by TCP payload
  * @dlen:		TCP payload length
  * @check:		Checksum, if already known
  * @seq:		Sequence number for this segment
@@ -958,11 +960,11 @@ static size_t tcp_fill_headers4(const struct tcp_tap_conn *conn,
  */
 static size_t tcp_fill_headers6(const struct tcp_tap_conn *conn,
 				struct tap_hdr *taph,
-				struct ipv6hdr *ip6h, struct tcphdr *th,
+				struct ipv6hdr *ip6h, struct tcp_payload_t *bp,
 				size_t dlen, uint32_t seq, bool no_tcp_csum)
 {
 	const struct flowside *tapside = TAPFLOW(conn);
-	size_t l4len = dlen + sizeof(*th);
+	size_t l4len = dlen + sizeof(bp->th);
 
 	ip6h->payload_len = htons(l4len);
 	ip6h->saddr = tapside->oaddr.a6;
@@ -976,12 +978,12 @@ static size_t 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(th, conn, seq);
+	tcp_fill_header(&bp->th, conn, seq);
 
 	if (no_tcp_csum)
-		th->check = 0;
+		bp->th.check = 0;
 	else
-		tcp_update_check_tcp6(ip6h, th);
+		tcp_update_check_tcp6(ip6h, bp);
 
 	tap_hdr_update(taph, l4len + sizeof(*ip6h) + sizeof(struct ethhdr));
 
diff --git a/tcp_buf.c b/tcp_buf.c
index ffbff5e4b485..238827b01d90 100644
--- a/tcp_buf.c
+++ b/tcp_buf.c
@@ -38,35 +38,6 @@
 	(c->mode == MODE_PASTA ? 1 : TCP_FRAMES_MEM)
 
 /* Static buffers */
-/**
- * struct tcp_payload_t - TCP header and data to send segments with payload
- * @th:		TCP header
- * @data:	TCP data
- */
-struct tcp_payload_t {
-	struct tcphdr th;
-	uint8_t data[IP_MAX_MTU - sizeof(struct tcphdr)];
-#ifdef __AVX2__
-} __attribute__ ((packed, aligned(32)));    /* For AVX2 checksum routines */
-#else
-} __attribute__ ((packed, aligned(__alignof__(unsigned int))));
-#endif
-
-/**
- * struct tcp_flags_t - TCP header and data to send zero-length
- *                      segments (flags)
- * @th:		TCP header
- * @opts	TCP options
- */
-struct tcp_flags_t {
-	struct tcphdr th;
-	char opts[OPT_MSS_LEN + OPT_WS_LEN + 1];
-#ifdef __AVX2__
-} __attribute__ ((packed, aligned(32)));
-#else
-} __attribute__ ((packed, aligned(__alignof__(unsigned int))));
-#endif
-
 /* Ethernet header for IPv4 frames */
 static struct ethhdr		tcp4_eth_src;
 
diff --git a/tcp_internal.h b/tcp_internal.h
index de06db1438d6..2f74ffeff8f3 100644
--- a/tcp_internal.h
+++ b/tcp_internal.h
@@ -63,6 +63,35 @@ enum tcp_iov_parts {
 	TCP_NUM_IOVS
 };
 
+/**
+ * struct tcp_payload_t - TCP header and data to send segments with payload
+ * @th:		TCP header
+ * @data:	TCP data
+ */
+struct tcp_payload_t {
+	struct tcphdr th;
+	uint8_t data[IP_MAX_MTU - sizeof(struct tcphdr)];
+#ifdef __AVX2__
+} __attribute__ ((packed, aligned(32)));    /* For AVX2 checksum routines */
+#else
+} __attribute__ ((packed, aligned(__alignof__(unsigned int))));
+#endif
+
+/**
+ * struct tcp_flags_t - TCP header and data to send zero-length
+ *                      segments (flags)
+ * @th:		TCP header
+ * @opts	TCP options
+ */
+struct tcp_flags_t {
+	struct tcphdr th;
+	char opts[OPT_MSS_LEN + OPT_WS_LEN + 1];
+#ifdef __AVX2__
+} __attribute__ ((packed, aligned(32)));
+#else
+} __attribute__ ((packed, aligned(__alignof__(unsigned int))));
+#endif
+
 extern char tcp_buf_discard [MAX_WINDOW];
 
 void conn_flag_do(const struct ctx *c, struct tcp_tap_conn *conn,
-- 
2.46.0


    