treewide: Standardise variable names for various packet lengths

At various points we need to track the lengths of a packet including or
excluding various different sets of headers.  We don't always use the same
variable names for doing so.  Worse in some places we use the same name
for different things: e.g. tcp_fill_headers[46]() use ip_len for the
length including the IP headers, but then tcp_send_flag() which calls it
uses it to mean the IP payload length only.

To improve clarity, standardise on these names:
   dlen:		L4 protocol payload length ("data length")
   l4len:		plen + length of L4 protocol header
   l3len:		l4len + length of IPv4/IPv6 header
   l2len:		l3len + length of L2 (ethernet) header

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

1 files changed, 69 insertions, 68 deletions

diff --git a/tap.c b/tap.c
index 230566b..c6864ac 100644
--- a/tap.c
+++ b/tap.c
@@ -70,11 +70,11 @@ static PACKET_POOL_NOINIT(pool_tap6, TAP_MSGS, pkt_buf);
  * tap_send_single() - Send a single frame
  * @c:		Execution context
  * @data:	Packet buffer
- * @len:	Total L2 packet length
+ * @l2len:	Total L2 packet length
  */
-void tap_send_single(const struct ctx *c, const void *data, size_t len)
+void tap_send_single(const struct ctx *c, const void *data, size_t l2len)
 {
-	uint32_t vnet_len = htonl(len);
+	uint32_t vnet_len = htonl(l2len);
 	struct iovec iov[2];
 	size_t iovcnt = 0;
 
@@ -85,7 +85,7 @@ void tap_send_single(const struct ctx *c, const void *data, size_t len)
 	}
 
 	iov[iovcnt].iov_base = (void *)data;
-	iov[iovcnt].iov_len = len;
+	iov[iovcnt].iov_len = l2len;
 	iovcnt++;
 
 	tap_send_frames(c, iov, iovcnt, 1);
@@ -141,27 +141,27 @@ static void *tap_push_l2h(const struct ctx *c, void *buf, uint16_t proto)
  * @c:		Execution context
  * @src:	IPv4 source address
  * @dst:	IPv4 destination address
- * @len:	L4 payload length
+ * @l4len:	IPv4 payload length
  * @proto:	L4 protocol number
  *
  * Return: pointer at which to write the packet's payload
  */
 static void *tap_push_ip4h(struct iphdr *ip4h, struct in_addr src,
-			   struct in_addr dst, size_t len, uint8_t proto)
+			   struct in_addr dst, size_t l4len, uint8_t proto)
 {
-	uint16_t tot_len = len + sizeof(*ip4h);
+	uint16_t l3len = l4len + sizeof(*ip4h);
 
 	ip4h->version = 4;
 	ip4h->ihl = sizeof(struct iphdr) / 4;
 	ip4h->tos = 0;
-	ip4h->tot_len = htons(tot_len);
+	ip4h->tot_len = htons(l3len);
 	ip4h->id = 0;
 	ip4h->frag_off = 0;
 	ip4h->ttl = 255;
 	ip4h->protocol = proto;
 	ip4h->saddr = src.s_addr;
 	ip4h->daddr = dst.s_addr;
-	ip4h->check = csum_ip4_header(tot_len, proto, src, dst);
+	ip4h->check = csum_ip4_header(l3len, proto, src, dst);
 	return ip4h + 1;
 }
 
@@ -173,25 +173,25 @@ static void *tap_push_ip4h(struct iphdr *ip4h, struct in_addr src,
  * @dst:	IPv4 destination address
  * @dport:	UDP destination port
  * @in:		UDP payload contents (not including UDP header)
- * @len:	UDP payload length (not including UDP header)
+ * @dlen:	UDP payload length (not including UDP header)
  */
 void tap_udp4_send(const struct ctx *c, struct in_addr src, in_port_t sport,
 		   struct in_addr dst, in_port_t dport,
-		   const void *in, size_t len)
+		   const void *in, size_t dlen)
 {
-	size_t udplen = len + sizeof(struct udphdr);
+	size_t l4len = dlen + sizeof(struct udphdr);
 	char buf[USHRT_MAX];
 	struct iphdr *ip4h = tap_push_l2h(c, buf, ETH_P_IP);
-	struct udphdr *uh = tap_push_ip4h(ip4h, src, dst, udplen, IPPROTO_UDP);
+	struct udphdr *uh = tap_push_ip4h(ip4h, src, dst, l4len, IPPROTO_UDP);
 	char *data = (char *)(uh + 1);
 
 	uh->source = htons(sport);
 	uh->dest = htons(dport);
-	uh->len = htons(udplen);
-	csum_udp4(uh, src, dst, in, len);
-	memcpy(data, in, len);
+	uh->len = htons(l4len);
+	csum_udp4(uh, src, dst, in, dlen);
+	memcpy(data, in, dlen);
 
-	tap_send_single(c, buf, len + (data - buf));
+	tap_send_single(c, buf, dlen + (data - buf));
 }
 
 /**
@@ -200,20 +200,20 @@ void tap_udp4_send(const struct ctx *c, struct in_addr src, in_port_t sport,
  * @src:	IPv4 source address
  * @dst:	IPv4 destination address
  * @in:		ICMP packet, including ICMP header
- * @len:	ICMP packet length, including ICMP header
+ * @l4len:	ICMP packet length, including ICMP header
  */
 void tap_icmp4_send(const struct ctx *c, struct in_addr src, struct in_addr dst,
-		    const void *in, size_t len)
+		    const void *in, size_t l4len)
 {
 	char buf[USHRT_MAX];
 	struct iphdr *ip4h = tap_push_l2h(c, buf, ETH_P_IP);
 	struct icmphdr *icmp4h = tap_push_ip4h(ip4h, src, dst,
-					       len, IPPROTO_ICMP);
+					       l4len, IPPROTO_ICMP);
 
-	memcpy(icmp4h, in, len);
-	csum_icmp4(icmp4h, icmp4h + 1, len - sizeof(*icmp4h));
+	memcpy(icmp4h, in, l4len);
+	csum_icmp4(icmp4h, icmp4h + 1, l4len - sizeof(*icmp4h));
 
-	tap_send_single(c, buf, len + ((char *)icmp4h - buf));
+	tap_send_single(c, buf, l4len + ((char *)icmp4h - buf));
 }
 
 /**
@@ -221,7 +221,7 @@ void tap_icmp4_send(const struct ctx *c, struct in_addr src, struct in_addr dst,
  * @c:		Execution context
  * @src:	IPv6 source address
  * @dst:	IPv6 destination address
- * @len:	L4 payload length
+ * @l4len:	L4 payload length
  * @proto:	L4 protocol number
  * @flow:	IPv6 flow identifier
  *
@@ -230,9 +230,9 @@ void tap_icmp4_send(const struct ctx *c, struct in_addr src, struct in_addr dst,
 static void *tap_push_ip6h(struct ipv6hdr *ip6h,
 			   const struct in6_addr *src,
 			   const struct in6_addr *dst,
-			   size_t len, uint8_t proto, uint32_t flow)
+			   size_t l4len, uint8_t proto, uint32_t flow)
 {
-	ip6h->payload_len = htons(len);
+	ip6h->payload_len = htons(l4len);
 	ip6h->priority = 0;
 	ip6h->version = 6;
 	ip6h->nexthdr = proto;
@@ -254,27 +254,27 @@ static void *tap_push_ip6h(struct ipv6hdr *ip6h,
  * @dport:	UDP destination port
  * @flow:	Flow label
  * @in:		UDP payload contents (not including UDP header)
- * @len:	UDP payload length (not including UDP header)
+ * @dlen:	UDP payload length (not including UDP header)
  */
 void tap_udp6_send(const struct ctx *c,
 		   const struct in6_addr *src, in_port_t sport,
 		   const struct in6_addr *dst, in_port_t dport,
-		   uint32_t flow, const void *in, size_t len)
+		   uint32_t flow, const void *in, size_t dlen)
 {
-	size_t udplen = len + sizeof(struct udphdr);
+	size_t l4len = dlen + sizeof(struct udphdr);
 	char buf[USHRT_MAX];
 	struct ipv6hdr *ip6h = tap_push_l2h(c, buf, ETH_P_IPV6);
 	struct udphdr *uh = tap_push_ip6h(ip6h, src, dst,
-					  udplen, IPPROTO_UDP, flow);
+					  l4len, IPPROTO_UDP, flow);
 	char *data = (char *)(uh + 1);
 
 	uh->source = htons(sport);
 	uh->dest = htons(dport);
-	uh->len = htons(udplen);
-	csum_udp6(uh, src, dst, in, len);
-	memcpy(data, in, len);
+	uh->len = htons(l4len);
+	csum_udp6(uh, src, dst, in, dlen);
+	memcpy(data, in, dlen);
 
-	tap_send_single(c, buf, len + (data - buf));
+	tap_send_single(c, buf, dlen + (data - buf));
 }
 
 /**
@@ -283,21 +283,21 @@ void tap_udp6_send(const struct ctx *c,
  * @src:	IPv6 source address
  * @dst:	IPv6 destination address
  * @in:		ICMP packet, including ICMP header
- * @len:	ICMP packet length, including ICMP header
+ * @l4len:	ICMP packet length, including ICMP header
  */
 void tap_icmp6_send(const struct ctx *c,
 		    const struct in6_addr *src, const struct in6_addr *dst,
-		    const void *in, size_t len)
+		    const void *in, size_t l4len)
 {
 	char buf[USHRT_MAX];
 	struct ipv6hdr *ip6h = tap_push_l2h(c, buf, ETH_P_IPV6);
-	struct icmp6hdr *icmp6h = tap_push_ip6h(ip6h, src, dst, len,
+	struct icmp6hdr *icmp6h = tap_push_ip6h(ip6h, src, dst, l4len,
 						IPPROTO_ICMPV6, 0);
 
-	memcpy(icmp6h, in, len);
-	csum_icmp6(icmp6h, src, dst, icmp6h + 1, len - sizeof(*icmp6h));
+	memcpy(icmp6h, in, l4len);
+	csum_icmp6(icmp6h, src, dst, icmp6h + 1, l4len - sizeof(*icmp6h));
 
-	tap_send_single(c, buf, len + ((char *)icmp6h - buf));
+	tap_send_single(c, buf, l4len + ((char *)icmp6h - buf));
 }
 
 /**
@@ -591,21 +591,21 @@ static int tap4_handler(struct ctx *c, const struct pool *in,
 	i = 0;
 resume:
 	for (seq_count = 0, seq = NULL; i < in->count; i++) {
-		size_t l2_len, l3_len, hlen, l4_len;
+		size_t l2len, l3len, hlen, l4len;
 		const struct ethhdr *eh;
 		const struct udphdr *uh;
 		struct iphdr *iph;
 		const char *l4h;
 
-		packet_get(in, i, 0, 0, &l2_len);
+		packet_get(in, i, 0, 0, &l2len);
 
-		eh = packet_get(in, i, 0, sizeof(*eh), &l3_len);
+		eh = packet_get(in, i, 0, sizeof(*eh), &l3len);
 		if (!eh)
 			continue;
 		if (ntohs(eh->h_proto) == ETH_P_ARP) {
 			PACKET_POOL_P(pkt, 1, in->buf, sizeof(pkt_buf));
 
-			packet_add(pkt, l2_len, (char *)eh);
+			packet_add(pkt, l2len, (char *)eh);
 			arp(c, pkt);
 			continue;
 		}
@@ -615,15 +615,15 @@ resume:
 			continue;
 
 		hlen = iph->ihl * 4UL;
-		if (hlen < sizeof(*iph) || htons(iph->tot_len) > l3_len ||
-		    hlen > l3_len)
+		if (hlen < sizeof(*iph) || htons(iph->tot_len) > l3len ||
+		    hlen > l3len)
 			continue;
 
 		/* We don't handle IP fragments, drop them */
 		if (tap4_is_fragment(iph, now))
 			continue;
 
-		l4_len = htons(iph->tot_len) - hlen;
+		l4len = htons(iph->tot_len) - hlen;
 
 		if (IN4_IS_ADDR_LOOPBACK(&iph->saddr) ||
 		    IN4_IS_ADDR_LOOPBACK(&iph->daddr)) {
@@ -638,7 +638,7 @@ resume:
 		if (iph->saddr && c->ip4.addr_seen.s_addr != iph->saddr)
 			c->ip4.addr_seen.s_addr = iph->saddr;
 
-		l4h = packet_get(in, i, sizeof(*eh) + hlen, l4_len, NULL);
+		l4h = packet_get(in, i, sizeof(*eh) + hlen, l4len, NULL);
 		if (!l4h)
 			continue;
 
@@ -650,7 +650,7 @@ resume:
 
 			tap_packet_debug(iph, NULL, NULL, 0, NULL, 1);
 
-			packet_add(pkt, l4_len, l4h);
+			packet_add(pkt, l4len, l4h);
 			icmp_tap_handler(c, PIF_TAP, AF_INET,
 					 &iph->saddr, &iph->daddr,
 					 pkt, now);
@@ -664,7 +664,7 @@ resume:
 		if (iph->protocol == IPPROTO_UDP) {
 			PACKET_POOL_P(pkt, 1, in->buf, sizeof(pkt_buf));
 
-			packet_add(pkt, l2_len, (char *)eh);
+			packet_add(pkt, l2len, (char *)eh);
 			if (dhcp(c, pkt))
 				continue;
 		}
@@ -713,7 +713,7 @@ resume:
 #undef L4_SET
 
 append:
-		packet_add((struct pool *)&seq->p, l4_len, l4h);
+		packet_add((struct pool *)&seq->p, l4len, l4h);
 	}
 
 	for (j = 0, seq = tap4_l4; j < seq_count; j++, seq++) {
@@ -765,7 +765,7 @@ static int tap6_handler(struct ctx *c, const struct pool *in,
 	i = 0;
 resume:
 	for (seq_count = 0, seq = NULL; i < in->count; i++) {
-		size_t l4_len, plen, check;
+		size_t l4len, plen, check;
 		struct in6_addr *saddr, *daddr;
 		const struct ethhdr *eh;
 		const struct udphdr *uh;
@@ -788,7 +788,7 @@ resume:
 		if (plen != check)
 			continue;
 
-		if (!(l4h = ipv6_l4hdr(in, i, sizeof(*eh), &proto, &l4_len)))
+		if (!(l4h = ipv6_l4hdr(in, i, sizeof(*eh), &proto, &l4len)))
 			continue;
 
 		if (IN6_IS_ADDR_LOOPBACK(saddr) || IN6_IS_ADDR_LOOPBACK(daddr)) {
@@ -816,7 +816,7 @@ resume:
 			if (c->no_icmp)
 				continue;
 
-			if (l4_len < sizeof(struct icmp6hdr))
+			if (l4len < sizeof(struct icmp6hdr))
 				continue;
 
 			if (ndp(c, (struct icmp6hdr *)l4h, saddr))
@@ -824,20 +824,20 @@ resume:
 
 			tap_packet_debug(NULL, ip6h, NULL, proto, NULL, 1);
 
-			packet_add(pkt, l4_len, l4h);
+			packet_add(pkt, l4len, l4h);
 			icmp_tap_handler(c, PIF_TAP, AF_INET6,
 					 saddr, daddr, pkt, now);
 			continue;
 		}
 
-		if (l4_len < sizeof(*uh))
+		if (l4len < sizeof(*uh))
 			continue;
 		uh = (struct udphdr *)l4h;
 
 		if (proto == IPPROTO_UDP) {
 			PACKET_POOL_P(pkt, 1, in->buf, sizeof(pkt_buf));
 
-			packet_add(pkt, l4_len, l4h);
+			packet_add(pkt, l4len, l4h);
 
 			if (dhcpv6(c, pkt, saddr, daddr))
 				continue;
@@ -888,7 +888,7 @@ resume:
 #undef L4_SET
 
 append:
-		packet_add((struct pool *)&seq->p, l4_len, l4h);
+		packet_add((struct pool *)&seq->p, l4len, l4h);
 	}
 
 	for (j = 0, seq = tap6_l4; j < seq_count; j++, seq++) {
@@ -971,7 +971,7 @@ redo:
 	}
 
 	while (n > (ssize_t)sizeof(uint32_t)) {
-		ssize_t len = ntohl(*(uint32_t *)p);
+		ssize_t l2len = ntohl(*(uint32_t *)p);
 
 		p += sizeof(uint32_t);
 		n -= sizeof(uint32_t);
@@ -979,19 +979,20 @@ redo:
 		/* At most one packet might not fit in a single read, and this
 		 * needs to be blocking.
 		 */
-		if (len > n) {
-			rem = recv(c->fd_tap, p + n, len - n, 0);
-			if ((n += rem) != len)
+		if (l2len > n) {
+			rem = recv(c->fd_tap, p + n, l2len - n, 0);
+			if ((n += rem) != l2len)
 				return;
 		}
 
 		/* Complete the partial read above before discarding a malformed
 		 * frame, otherwise the stream will be inconsistent.
 		 */
-		if (len < (ssize_t)sizeof(*eh) || len > (ssize_t)ETH_MAX_MTU)
+		if (l2len < (ssize_t)sizeof(*eh) ||
+		    l2len > (ssize_t)ETH_MAX_MTU)
 			goto next;
 
-		pcap(p, len);
+		pcap(p, l2len);
 
 		eh = (struct ethhdr *)p;
 
@@ -1003,18 +1004,18 @@ redo:
 		switch (ntohs(eh->h_proto)) {
 		case ETH_P_ARP:
 		case ETH_P_IP:
-			packet_add(pool_tap4, len, p);
+			packet_add(pool_tap4, l2len, p);
 			break;
 		case ETH_P_IPV6:
-			packet_add(pool_tap6, len, p);
+			packet_add(pool_tap6, l2len, p);
 			break;
 		default:
 			break;
 		}
 
 next:
-		p += len;
-		n -= len;
+		p += l2len;
+		n -= l2len;
 	}
 
 	tap4_handler(c, pool_tap4, now);