[PATCH v9 19/20] tcp: Merge tcp_update_check_tcp[46]()

[David Gibson <david@gibson.dropbear.id.au>]

The only reason we need separate functions for the IPv4 and IPv6 case is
to calculate the checksum of the IP pseudo-header, which is different for
the two cases.  However, the caller already knows which path it's on and
can access the values needed for the pseudo-header partial sum more easily
than tcp_update_check_tcp[46]() can.

So, merge these functions into a single tcp_update_csum() function that
just takes the pseudo-header partial sum, calculated in the caller.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
---
 tcp.c          | 65 +++++++++++++++++---------------------------------
 tcp_internal.h |  9 +++----
 tcp_vu.c       | 18 +++++++++-----
 3 files changed, 37 insertions(+), 55 deletions(-)

diff --git a/tcp.c b/tcp.c
index 5e26243..297eb8c 100644
--- a/tcp.c
+++ b/tcp.c
@@ -753,50 +753,20 @@ static void tcp_sock_set_bufsize(const struct ctx *c, int s)
 }
 
 /**
- * tcp_update_check_tcp4() - Calculate TCP checksum for IPv4
- * @iph:	IPv4 header
+ * tcp_update_csum() - Calculate TCP checksum
+ * @psum:	Unfolded partial checksum of the IPv4 or IPv6 pseudo-header
  * @th:		TCP header (updated)
  * @iov:	IO vector containing the TCP payload
  * @iov_cnt:	Length of @iov
  * @doffset:	TCP payload offset in @iov
  */
-void tcp_update_check_tcp4(const struct iphdr *iph, struct tcphdr *th,
-			   const struct iovec *iov, int iov_cnt,
-			   size_t doffset)
+void tcp_update_csum(uint32_t psum, struct tcphdr *th,
+		     const struct iovec *iov, int iov_cnt,
+		     size_t doffset)
 {
-	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;
-
-	sum = proto_ipv4_header_psum(l4len, IPPROTO_TCP, saddr, daddr);
-
-	th->check = 0;
-	sum = csum_unfolded(th, sizeof(*th), sum);
-	th->check = csum_iov(iov, iov_cnt, doffset, sum);
-}
-
-/**
- * tcp_update_check_tcp6() - Calculate TCP checksum for IPv6
- * @ip6h:	IPv6 header
- * @th:		TCP header (updated)
- * @iov:	IO vector containing the TCP payload
- * @iov_cnt:	Length of @iov
- * @doffset:	TCP payload offset in @iov
- */
-void tcp_update_check_tcp6(const struct ipv6hdr *ip6h, struct tcphdr *th,
-			   const struct iovec *iov, int iov_cnt,
-			   size_t doffset)
-{
-	uint16_t l4len = ntohs(ip6h->payload_len);
-	uint32_t sum;
-
-	sum = proto_ipv6_header_psum(l4len, IPPROTO_TCP, &ip6h->saddr,
-				     &ip6h->daddr);
-
 	th->check = 0;
-	sum = csum_unfolded(th, sizeof(*th), sum);
-	th->check = csum_iov(iov, iov_cnt, doffset, sum);
+	psum = csum_unfolded(th, sizeof(*th), psum);
+	th->check = csum_iov(iov, iov_cnt, doffset, psum);
 }
 
 /**
@@ -948,10 +918,14 @@ void tcp_fill_headers4(const struct tcp_tap_conn *conn,
 
 	tcp_fill_header(th, conn, seq);
 
-	if (no_tcp_csum)
+	if (no_tcp_csum) {
 		th->check = 0;
-	else
-		tcp_update_check_tcp4(iph, th, iov, iov_cnt, doffset);
+	} else {
+		uint32_t psum = proto_ipv4_header_psum(l4len, IPPROTO_TCP,
+						       *src4, *dst4);
+
+		tcp_update_csum(psum, th, iov, iov_cnt, doffset);
+	}
 
 	tap_hdr_update(taph, l3len + sizeof(struct ethhdr));
 }
@@ -993,10 +967,15 @@ void tcp_fill_headers6(const struct tcp_tap_conn *conn,
 
 	tcp_fill_header(th, conn, seq);
 
-	if (no_tcp_csum)
+	if (no_tcp_csum) {
 		th->check = 0;
-	else
-		tcp_update_check_tcp6(ip6h, th, iov, iov_cnt, doffset);
+	} else {
+		uint32_t psum = proto_ipv6_header_psum(l4len, IPPROTO_TCP,
+						       &ip6h->saddr,
+						       &ip6h->daddr);
+
+		tcp_update_csum(psum, th, iov, iov_cnt, doffset);
+	}
 
 	tap_hdr_update(taph, l4len + sizeof(*ip6h) + sizeof(struct ethhdr));
 }
diff --git a/tcp_internal.h b/tcp_internal.h
index 8f9267c..a2de15a 100644
--- a/tcp_internal.h
+++ b/tcp_internal.h
@@ -177,12 +177,9 @@ void tcp_rst_do(const struct ctx *c, struct tcp_tap_conn *conn);
 
 struct tcp_info_linux;
 
-void tcp_update_check_tcp4(const struct iphdr *iph, struct tcphdr *th,
-			   const struct iovec *iov, int iov_cnt,
-			   size_t doffset);
-void tcp_update_check_tcp6(const struct ipv6hdr *ip6h, struct tcphdr *th,
-			   const struct iovec *iov, int iov_cnt,
-			   size_t doffset);
+void tcp_update_csum(uint32_t psum, struct tcphdr *th,
+		     const struct iovec *iov, int iov_cnt,
+		     size_t doffset);
 void tcp_fill_headers4(const struct tcp_tap_conn *conn,
 		       struct tap_hdr *taph, struct iphdr *iph,
 		       struct tcphdr *th,
diff --git a/tcp_vu.c b/tcp_vu.c
index bf45c74..916e35d 100644
--- a/tcp_vu.c
+++ b/tcp_vu.c
@@ -67,20 +67,26 @@ static void tcp_vu_update_check(const struct flowside *tapside,
 			        struct iovec *iov, int iov_used)
 {
 	char *base = iov[0].iov_base;
+	struct tcphdr *th;
+	uint32_t psum;
 
 	if (inany_v4(&tapside->oaddr)) {
-		struct tcphdr *th = vu_payloadv4(base);
+		const struct in_addr *src4 = inany_v4(&tapside->oaddr);
+		const struct in_addr *dst4 = inany_v4(&tapside->eaddr);
 		const struct iphdr *iph = vu_ip(base);
+		size_t l4len = ntohs(iph->tot_len) - sizeof(*th);
 
-		tcp_update_check_tcp4(iph, th, iov, iov_used,
-				      (char *)(th + 1) - base);
+		th = vu_payloadv4(base);
+		psum = proto_ipv4_header_psum(l4len, IPPROTO_TCP, *src4, *dst4);
 	} else {
-		struct tcphdr *th = vu_payloadv6(base);
 		const struct ipv6hdr *ip6h = vu_ip(base);
+		size_t l4len = ntohs(ip6h->payload_len);
 
-		tcp_update_check_tcp6(ip6h, th, iov, iov_used,
-				      (char *)(th + 1) - base);
+		th = vu_payloadv6(base);
+		psum = proto_ipv6_header_psum(l4len, IPPROTO_TCP,
+					      &ip6h->saddr, &ip6h->daddr);
 	}
+	tcp_update_csum(psum, th, iov, iov_used, (char *)(th + 1) - base);
 }
 
 /**
-- 
2.47.0