[PATCH v2 6/8] checksum: use csum_ip4_header() in udp.c and tcp.c

[Laurent Vivier <lvivier@redhat.com>]

We can find the same function to compute the IPv4 header
checksum in tcp.c, udp.c and tap.c

Use the function defined for tap.c, csum_ip4_header(), but
with the code used in tcp.c and udp.c as it doesn't need a fully
initialiazed IPv4 header, only protocol, tot_len, saddr and daddr.

Signed-off-by: Laurent Vivier <lvivier@redhat.com>
---

Notes:
    v2:
      - use csum_ip4_header() from checksum.c
      - use code from tcp.c and udp.c in csum_ip4_header()
      - use "const struct iphfr *", check is not updated by the
        function but by the caller.

 checksum.c | 16 ++++++++++++----
 checksum.h |  2 +-
 tap.c      |  2 +-
 tcp.c      | 22 +---------------------
 udp.c      | 23 +++++------------------
 5 files changed, 20 insertions(+), 45 deletions(-)

diff --git a/checksum.c b/checksum.c
index ac2bc49f7eb0..5613187a1c82 100644
--- a/checksum.c
+++ b/checksum.c
@@ -57,6 +57,7 @@
 #include <linux/icmpv6.h>
 
 #include "util.h"
+#include "ip.h"
 
 /* Checksums are optional for UDP over IPv4, so we usually just set
  * them to 0.  Change this to 1 to calculate real UDP over IPv4
@@ -115,13 +116,20 @@ uint16_t csum_fold(uint32_t sum)
 uint16_t csum(const void *buf, size_t len, uint32_t init);
 
 /**
- * csum_ip4_header() - Calculate and set IPv4 header checksum
+ * csum_ip4_header() - Calculate IPv4 header checksum
  * @ip4h:	IPv4 header
  */
-void csum_ip4_header(struct iphdr *ip4h)
+uint16_t csum_ip4_header(const struct iphdr *ip4h)
 {
-	ip4h->check = 0;
-	ip4h->check = csum(ip4h, (size_t)ip4h->ihl * 4, 0);
+	uint32_t sum = L2_BUF_IP4_PSUM(ip4h->protocol);
+
+	sum += ip4h->tot_len;
+	sum += (ip4h->saddr >> 16) & 0xffff;
+	sum += ip4h->saddr & 0xffff;
+	sum += (ip4h->daddr >> 16) & 0xffff;
+	sum += ip4h->daddr & 0xffff;
+
+	return ~csum_fold(sum);
 }
 
 /**
diff --git a/checksum.h b/checksum.h
index 6a20297a5826..b87ecd720df5 100644
--- a/checksum.h
+++ b/checksum.h
@@ -13,7 +13,7 @@ struct icmp6hdr;
 uint32_t sum_16b(const void *buf, size_t len);
 uint16_t csum_fold(uint32_t sum);
 uint16_t csum_unaligned(const void *buf, size_t len, uint32_t init);
-void csum_ip4_header(struct iphdr *ip4h);
+uint16_t csum_ip4_header(const struct iphdr *ip4h);
 void csum_udp4(struct udphdr *udp4hr,
 	       struct in_addr saddr, struct in_addr daddr,
 	       const void *payload, size_t len);
diff --git a/tap.c b/tap.c
index 3ea03f720d6d..70f36a55314f 100644
--- a/tap.c
+++ b/tap.c
@@ -160,7 +160,7 @@ static void *tap_push_ip4h(char *buf, struct in_addr src, struct in_addr dst,
 	ip4h->protocol = proto;
 	ip4h->saddr = src.s_addr;
 	ip4h->daddr = dst.s_addr;
-	csum_ip4_header(ip4h);
+	ip4h->check = csum_ip4_header(ip4h);
 	return ip4h + 1;
 }
 
diff --git a/tcp.c b/tcp.c
index 45ef5146729a..35e240f4ffc3 100644
--- a/tcp.c
+++ b/tcp.c
@@ -934,23 +934,6 @@ static void tcp_sock_set_bufsize(const struct ctx *c, int s)
 		trace("TCP: failed to set SO_SNDBUF to %i", v);
 }
 
-/**
- * tcp_update_check_ip4() - Update IPv4 with variable parts from stored one
- * @buf:	L2 packet buffer with final IPv4 header
- */
-static void tcp_update_check_ip4(struct tcp4_l2_buf_t *buf)
-{
-	uint32_t sum = L2_BUF_IP4_PSUM(IPPROTO_TCP);
-
-	sum += buf->iph.tot_len;
-	sum += (buf->iph.saddr >> 16) & 0xffff;
-	sum += buf->iph.saddr & 0xffff;
-	sum += (buf->iph.daddr >> 16) & 0xffff;
-	sum += buf->iph.daddr & 0xffff;
-
-	buf->iph.check = (uint16_t)~csum_fold(sum);
-}
-
 /**
  * tcp_update_check_tcp4() - Update TCP checksum from stored one
  * @buf:	L2 packet buffer with final IPv4 header
@@ -1393,10 +1376,7 @@ do {									\
 		b->iph.saddr = a4->s_addr;
 		b->iph.daddr = c->ip4.addr_seen.s_addr;
 
-		if (check)
-			b->iph.check = *check;
-		else
-			tcp_update_check_ip4(b);
+		b->iph.check = check ? *check : csum_ip4_header(&b->iph);
 
 		SET_TCP_HEADER_COMMON_V4_V6(b, conn, seq);
 
diff --git a/udp.c b/udp.c
index d514c864ab5b..e645c800a823 100644
--- a/udp.c
+++ b/udp.c
@@ -270,23 +270,6 @@ static void udp_invert_portmap(struct udp_port_fwd *fwd)
 	}
 }
 
-/**
- * udp_update_check4() - Update checksum with variable parts from stored one
- * @buf:	L2 packet buffer with final IPv4 header
- */
-static void udp_update_check4(struct udp4_l2_buf_t *buf)
-{
-	uint32_t sum = L2_BUF_IP4_PSUM(IPPROTO_UDP);
-
-	sum += buf->iph.tot_len;
-	sum += (buf->iph.saddr >> 16) & 0xffff;
-	sum += buf->iph.saddr & 0xffff;
-	sum += (buf->iph.daddr >> 16) & 0xffff;
-	sum += buf->iph.daddr & 0xffff;
-
-	buf->iph.check = (uint16_t)~csum_fold(sum);
-}
-
 /**
  * udp_update_l2_buf() - Update L2 buffers with Ethernet and IPv4 addresses
  * @eth_d:	Ethernet destination address, NULL if unchanged
@@ -579,6 +562,9 @@ static void udp_splice_sendfrom(const struct ctx *c, unsigned start, unsigned n,
  *
  * Return: size of tap frame with headers
  */
+#pragma GCC diagnostic push
+/* ignore unaligned pointer value warning for &b->iph */
+#pragma GCC diagnostic ignored "-Waddress-of-packed-member"
 static size_t udp_update_hdr4(const struct ctx *c, int n, in_port_t dstport,
 			      const struct timespec *now)
 {
@@ -614,13 +600,14 @@ static size_t udp_update_hdr4(const struct ctx *c, int n, in_port_t dstport,
 		b->iph.saddr = b->s_in.sin_addr.s_addr;
 	}
 
-	udp_update_check4(b);
+	b->iph.check = csum_ip4_header(&b->iph);
 	b->uh.source = b->s_in.sin_port;
 	b->uh.dest = htons(dstport);
 	b->uh.len = htons(udp4_l2_mh_sock[n].msg_len + sizeof(b->uh));
 
 	return tap_iov_len(c, &b->taph, ip_len);
 }
+#pragma GCC diagnostic pop
 
 /**
  * udp_update_hdr6() - Update headers for one IPv6 datagram
-- 
@@ -270,23 +270,6 @@ static void udp_invert_portmap(struct udp_port_fwd *fwd)
 	}
 }
 
-/**
- * udp_update_check4() - Update checksum with variable parts from stored one
- * @buf:	L2 packet buffer with final IPv4 header
- */
-static void udp_update_check4(struct udp4_l2_buf_t *buf)
-{
-	uint32_t sum = L2_BUF_IP4_PSUM(IPPROTO_UDP);
-
-	sum += buf->iph.tot_len;
-	sum += (buf->iph.saddr >> 16) & 0xffff;
-	sum += buf->iph.saddr & 0xffff;
-	sum += (buf->iph.daddr >> 16) & 0xffff;
-	sum += buf->iph.daddr & 0xffff;
-
-	buf->iph.check = (uint16_t)~csum_fold(sum);
-}
-
 /**
  * udp_update_l2_buf() - Update L2 buffers with Ethernet and IPv4 addresses
  * @eth_d:	Ethernet destination address, NULL if unchanged
@@ -579,6 +562,9 @@ static void udp_splice_sendfrom(const struct ctx *c, unsigned start, unsigned n,
  *
  * Return: size of tap frame with headers
  */
+#pragma GCC diagnostic push
+/* ignore unaligned pointer value warning for &b->iph */
+#pragma GCC diagnostic ignored "-Waddress-of-packed-member"
 static size_t udp_update_hdr4(const struct ctx *c, int n, in_port_t dstport,
 			      const struct timespec *now)
 {
@@ -614,13 +600,14 @@ static size_t udp_update_hdr4(const struct ctx *c, int n, in_port_t dstport,
 		b->iph.saddr = b->s_in.sin_addr.s_addr;
 	}
 
-	udp_update_check4(b);
+	b->iph.check = csum_ip4_header(&b->iph);
 	b->uh.source = b->s_in.sin_port;
 	b->uh.dest = htons(dstport);
 	b->uh.len = htons(udp4_l2_mh_sock[n].msg_len + sizeof(b->uh));
 
 	return tap_iov_len(c, &b->taph, ip_len);
 }
+#pragma GCC diagnostic pop
 
 /**
  * udp_update_hdr6() - Update headers for one IPv6 datagram
-- 
2.42.0