Assemble outgoing packets using iovec to combine the (optional)

ethernet header, the ip header, the udp header and the packet.
Rather than manually concatenating the headers and then using iovec
to bundle in the packet. Eliminates some memcpy()s and convoluted
data copying.

1 files changed, 47 insertions, 17 deletions

diff --git a/sbin/dhclient/bpf.c b/sbin/dhclient/bpf.c
index 7620d048cac..d0eaa8f745e 100644
--- a/sbin/dhclient/bpf.c
+++ b/sbin/dhclient/bpf.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: bpf.c,v 1.30 2013/12/06 23:40:48 krw Exp $	*/
+/*	$OpenBSD: bpf.c,v 1.31 2013/12/12 00:22:06 krw Exp $	*/
 
 /* BPF socket interface code, originally contributed by Archie Cobbs. */
 
@@ -264,35 +264,65 @@ ssize_t
 send_packet(struct in_addr from, struct sockaddr_in *to,
     struct ether_addr *hto)
 {
-#define IOVCNT		2
-	unsigned char buf[256];
-	struct iovec iov[IOVCNT];
+	struct ether_header eh;
+	struct ip ip;
+	struct udphdr udp;
+	struct iovec iov[4];
 	struct msghdr msg;
+	unsigned char *data;
 	ssize_t result;
-	int bufp = 0;
+	int iovcnt = 0, len;
 
 	if (to->sin_addr.s_addr == INADDR_BROADCAST) {
-		assemble_hw_header(buf, &bufp, hto);
+		assemble_eh_header(&eh, hto);
+		iov[0].iov_base = &eh;
+		iov[0].iov_len = sizeof(eh);
+		iovcnt++;
 	}
 
-	assemble_udp_ip_header(buf, &bufp, from.s_addr,
-	    to->sin_addr.s_addr, to->sin_port,
-	    (unsigned char *)&client->bootrequest_packet,
-	    client->bootrequest_packet_length);
-
-	iov[0].iov_base = (char *)buf;
-	iov[0].iov_len = bufp;
-	iov[1].iov_base = (char *)&client->bootrequest_packet;
-	iov[1].iov_len = client->bootrequest_packet_length;
+	data = (unsigned char *)&client->bootrequest_packet;
+	len = client->bootrequest_packet_length;
+
+	ip.ip_v = 4;
+	ip.ip_hl = 5;
+	ip.ip_tos = IPTOS_LOWDELAY;
+	ip.ip_len = htons(sizeof(ip) + sizeof(udp) + len);
+	ip.ip_id = 0;
+	ip.ip_off = 0;
+	ip.ip_ttl = 128;
+	ip.ip_p = IPPROTO_UDP;
+	ip.ip_sum = 0;
+	ip.ip_src.s_addr = from.s_addr;
+	ip.ip_dst.s_addr = to->sin_addr.s_addr;
+	ip.ip_sum = wrapsum(checksum((unsigned char *)&ip, sizeof(ip), 0));
+	iov[iovcnt].iov_base = &ip;
+	iov[iovcnt].iov_len = sizeof(ip);
+	iovcnt++;
+
+	udp.uh_sport = htons(LOCAL_PORT);
+	udp.uh_dport = to->sin_port;
+	udp.uh_ulen = htons(sizeof(udp) + len);
+	udp.uh_sum = 0;
+	udp.uh_sum = wrapsum(checksum((unsigned char *)&udp, sizeof(udp),
+	    checksum(data, len, checksum((unsigned char *)&ip.ip_src,
+	    2 * sizeof(ip.ip_src),
+	    IPPROTO_UDP + (u_int32_t)ntohs(udp.uh_ulen)))));
+	iov[iovcnt].iov_base = &udp;
+	iov[iovcnt].iov_len = sizeof(udp);
+	iovcnt++;
+
+	iov[iovcnt].iov_base = data;
+	iov[iovcnt].iov_len = len;
+	iovcnt++;
 
 	if (to->sin_addr.s_addr == INADDR_BROADCAST) {
-		result = writev(ifi->wfdesc, iov, IOVCNT);
+		result = writev(ifi->wfdesc, iov, iovcnt);
 	} else {
 		memset(&msg, 0, sizeof(msg));
 		msg.msg_name = (struct sockaddr *)to;
 		msg.msg_namelen = sizeof(*to);
 		msg.msg_iov = iov;
-		msg.msg_iovlen = IOVCNT;
+		msg.msg_iovlen = iovcnt;
 		result = sendmsg(ifi->ufdesc, &msg, 0);
 	}