udp: Use abstracted tap header

Update the UDP code to use the tap layer abstractions for initializing and
updating the L2 and lower headers.  This will make adding other tap
backends in future easier.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

udp.c

@@ -169,8 +169,7 @@ static uint8_t udp_act[IP_VERSIONS][UDP_ACT_TYPE_MAX][DIV_ROUND_UP(NUM_PORTS, 8)
  * udp4_l2_buf_t - Pre-cooked IPv4 packet buffers for tap connections
  * @s_in:	Source socket address, filled in by recvmmsg()
  * @psum:	Partial IP header checksum (excluding tot_len and saddr)
- * @vnet_len:	4-byte qemu vnet buffer length descriptor, only for passt mode
+ * @taph:	Tap-level headers (partially pre-filled)
- * @eh:		Pre-filled Ethernet header
  * @iph:	Pre-filled IP header (except for tot_len and saddr)
  * @uh:		Headroom for UDP header
  * @data:	Storage for UDP payload
@@ -179,8 +178,7 @@ static struct udp4_l2_buf_t {
 	struct sockaddr_in s_in;
 	uint32_t psum;
 
-	uint32_t vnet_len;
+	struct tap_hdr taph;
-	struct ethhdr eh;
 	struct iphdr iph;
 	struct udphdr uh;
 	uint8_t data[USHRT_MAX -
@@ -191,8 +189,7 @@ udp4_l2_buf[UDP_MAX_FRAMES];
 /**
  * udp6_l2_buf_t - Pre-cooked IPv6 packet buffers for tap connections
  * @s_in6:	Source socket address, filled in by recvmmsg()
- * @vnet_len:	4-byte qemu vnet buffer length descriptor, only for passt mode
+ * @taph:	Tap-level headers (partially pre-filled)
- * @eh:		Pre-filled Ethernet header
  * @ip6h:	Pre-filled IP header (except for payload_len and addresses)
  * @uh:		Headroom for UDP header
  * @data:	Storage for UDP payload
@@ -205,8 +202,7 @@ struct udp6_l2_buf_t {
 			  sizeof(uint32_t))];
 #endif
 
-	uint32_t vnet_len;
+	struct tap_hdr taph;
-	struct ethhdr eh;
 	struct ipv6hdr ip6h;
 	struct udphdr uh;
 	uint8_t data[USHRT_MAX -
@@ -294,15 +290,8 @@ void udp_update_l2_buf(const unsigned char *eth_d, const unsigned char *eth_s,
 		struct udp4_l2_buf_t *b4 = &udp4_l2_buf[i];
 		struct udp6_l2_buf_t *b6 = &udp6_l2_buf[i];
 
-		if (eth_d) {
+		tap_update_mac(&b4->taph, eth_d, eth_s);
-			memcpy(b4->eh.h_dest, eth_d, ETH_ALEN);
+		tap_update_mac(&b6->taph, eth_d, eth_s);
-			memcpy(b6->eh.h_dest, eth_d, ETH_ALEN);
-		}
-
-		if (eth_s) {
-			memcpy(b4->eh.h_source, eth_s, ETH_ALEN);
-			memcpy(b6->eh.h_source, eth_s, ETH_ALEN);
-		}
 
 		if (ip_da) {
 			b4->iph.daddr = ip_da->s_addr;
@@ -329,7 +318,7 @@ static void udp_sock4_iov_init(const struct ctx *c)
 
 	for (i = 0; i < ARRAY_SIZE(udp4_l2_buf); i++) {
 		udp4_l2_buf[i] = (struct udp4_l2_buf_t) {
-			.eh = L2_BUF_ETH_INIT(ETH_P_IP),
+			.taph = TAP_HDR_INIT(ETH_P_IP),
 			.iph = L2_BUF_IP4_INIT(IPPROTO_UDP)
 		};
 	}
@@ -346,15 +335,12 @@ static void udp_sock4_iov_init(const struct ctx *c)
 		mh->msg_iovlen			= 1;
 	}
 
-	for (i = 0, h = udp4_l2_mh_tap; i < UDP_MAX_FRAMES; i++, h++) {
+	for (i = 0; i < UDP_MAX_FRAMES; i++) {
-		struct msghdr *mh = &h->msg_hdr;
+		struct msghdr *mh = &udp4_l2_mh_tap[i].msg_hdr;
+		struct iovec *iov = &udp4_l2_iov_tap[i];
 
-		if (c->mode == MODE_PASTA)
+		iov->iov_base	= tap_iov_base(c, &udp4_l2_buf[i].taph);
-			udp4_l2_iov_tap[i].iov_base	= &udp4_l2_buf[i].eh;
+		mh->msg_iov	= iov;
-		else
-			udp4_l2_iov_tap[i].iov_base	= &udp4_l2_buf[i].vnet_len;
-
-		mh->msg_iov			= &udp4_l2_iov_tap[i];
 		mh->msg_iovlen	= 1;
 	}
 }
@@ -370,7 +356,7 @@ static void udp_sock6_iov_init(const struct ctx *c)
 
 	for (i = 0; i < ARRAY_SIZE(udp6_l2_buf); i++) {
 		udp6_l2_buf[i] = (struct udp6_l2_buf_t) {
-			.eh = L2_BUF_ETH_INIT(ETH_P_IPV6),
+			.taph = TAP_HDR_INIT(ETH_P_IPV6),
 			.ip6h = L2_BUF_IP6_INIT(IPPROTO_UDP)
 		};
 	}
@@ -387,15 +373,12 @@ static void udp_sock6_iov_init(const struct ctx *c)
 		mh->msg_iovlen			= 1;
 	}
 
-	for (i = 0, h = udp6_l2_mh_tap; i < UDP_MAX_FRAMES; i++, h++) {
+	for (i = 0; i < UDP_MAX_FRAMES; i++) {
-		struct msghdr *mh = &h->msg_hdr;
+		struct msghdr *mh = &udp6_l2_mh_tap[i].msg_hdr;
+		struct iovec *iov = &udp6_l2_iov_tap[i];
 
-		if (c->mode == MODE_PASTA)
+		iov->iov_base	= tap_iov_base(c, &udp6_l2_buf[i].taph);
-			udp6_l2_iov_tap[i].iov_base	= &udp6_l2_buf[i].eh;
+		mh->msg_iov	= iov;
-		else
-			udp6_l2_iov_tap[i].iov_base	= &udp6_l2_buf[i].vnet_len;
-
-		mh->msg_iov			= &udp6_l2_iov_tap[i];
 		mh->msg_iovlen	= 1;
 	}
 }
@@ -607,8 +590,8 @@ static size_t udp_update_hdr4(const struct ctx *c, int n, in_port_t dstport,
 			      const struct timespec *now)
 {
 	struct udp4_l2_buf_t *b = &udp4_l2_buf[n];
-	size_t ip_len, buf_len;
 	in_port_t src_port;
+	size_t ip_len;
 
 	ip_len = udp4_l2_mh_sock[n].msg_len + sizeof(b->iph) + sizeof(b->uh);
 
@@ -642,14 +625,7 @@ static size_t udp_update_hdr4(const struct ctx *c, int n, in_port_t dstport,
 	b->uh.dest = htons(dstport);
 	b->uh.len = htons(udp4_l2_mh_sock[n].msg_len + sizeof(b->uh));
 
-	buf_len = ip_len + sizeof(b->eh);
+	return tap_iov_len(c, &b->taph, ip_len);
-
-	if (c->mode == MODE_PASST) {
-		b->vnet_len = htonl(buf_len);
-		buf_len += sizeof(b->vnet_len);
-	}
-
-	return buf_len;
 }
 
 /**
@@ -665,9 +641,9 @@ static size_t udp_update_hdr6(const struct ctx *c, int n, in_port_t dstport,
 			      const struct timespec *now)
 {
 	struct udp6_l2_buf_t *b = &udp6_l2_buf[n];
-	size_t ip_len, buf_len;
 	struct in6_addr *src;
 	in_port_t src_port;
+	size_t ip_len;
 
 	src = &b->s_in6.sin6_addr;
 	src_port = ntohs(b->s_in6.sin6_port);
@@ -724,14 +700,7 @@ static size_t udp_update_hdr6(const struct ctx *c, int n, in_port_t dstport,
 	b->ip6h.nexthdr = IPPROTO_UDP;
 	b->ip6h.hop_limit = 255;
 
-	buf_len = ip_len + sizeof(b->eh);
+	return tap_iov_len(c, &b->taph, ip_len);
-
-	if (c->mode == MODE_PASST) {
-		b->vnet_len = htonl(buf_len);
-		buf_len += sizeof(b->vnet_len);
-	}
-
-	return buf_len;
 }
 
 /**

util.h

@@ -102,13 +102,6 @@ int do_clone(int (*fn)(void *), char *stack_area, size_t stack_size, int flags,
 			 (void *)(arg));				\
 	} while (0)
 
-#define L2_BUF_ETH_INIT(proto)						\
-	{								\
-		.h_dest		= { 0 },				\
-		.h_source	= { 0 },				\
-		.h_proto	= htons_constant(proto),		\
-	}
-
 #define L2_BUF_IP4_INIT(proto)						\
 	{								\
 		.version	= 4,					\