isc-dhcp-4.3.1_dhcrelay-custom-circuit_id-remote_id-and-bridge-iface-support.patch

This patch adds the following functionality to dhcrelay in isc-dhcp v4.3.1-6:
* Add customizable Circuit ID and Remote ID fields
* Support for obtaining name of physical interface of interfaces that are part of a bridge interface

diff -ruN a/isc-dhcp/relay/dhcrelay.c b/isc-dhcp/relay/dhcrelay.c
--- a/isc-dhcp/relay/dhcrelay.c	2014-08-06 22:35:02.000000000 +0000
+++ b/isc-dhcp/relay/dhcrelay.c	2017-06-08 21:39:53.856192546 +0000
@@ -73,6 +73,8 @@
 				   did not match any known circuit ID. */
 int missing_circuit_id = 0;	/* Circuit ID option in matching RAI option
 				   was missing. */
+const char *agent_circuit_id_fmt = NULL; /* Circuit ID custom format string. */
+const char *agent_remote_id_fmt = NULL;  /* Remote ID custom format string. */
 int max_hop_count = 10;		/* Maximum hop count */
 
 #ifdef DHCPv6
@@ -140,9 +142,19 @@
 static const char url[] =
 "For info, please visit https://www.isc.org/software/dhcp/";
 
+#define DHCRELAY_OPTION82_USAGE \
+"circuit_id/remote_id interpreted sequences are:\n" \
+"\n" \
+"  %%%%  A single %%\n" \
+"  %%h  Hostname of device\n" \
+"  %%p  Name of interface that generated the request\n" \
+"  %%P  Hardware address of interface that generated the request\n" \
+"  %%C  Client hardware address\n" \
+"  %%I  DHCP relay agent IP Address\n" \
+
 #ifdef DHCPv6
 #define DHCRELAY_USAGE \
-"Usage: dhcrelay [-4] [-d] [-q] [-a] [-D]\n"\
+"Usage: dhcrelay [-4] [-d] [-q] [-a <circuit_id> <remote_id>] [-D]\n"\
 "                     [-A <length>] [-c <hops>] [-p <port>]\n" \
 "                     [-pf <pid-file>] [--no-pid]\n"\
 "                     [-m append|replace|forward|discard]\n" \
@@ -154,14 +166,15 @@
 "                     -l lower0 [ ... -l lowerN]\n" \
 "                     -u upper0 [ ... -u upperN]\n" \
 "       lower (client link): [address%%]interface[#index]\n" \
-"       upper (server link): [address%%]interface"
+"       upper (server link): [address%%]interface\n\n" DHCRELAY_OPTION82_USAGE
 #else
 #define DHCRELAY_USAGE \
-"Usage: dhcrelay [-d] [-q] [-a] [-D] [-A <length>] [-c <hops>] [-p <port>]\n" \
-"                [-pf <pid-file>] [--no-pid]\n" \
+"Usage: dhcrelay [-d] [-q] [-a <circuit_id> <remote_id>] [-D]\n" \
+"                [-A <length>] [-c <hops>] [-p <port>]\n" \
+"                [-pf <pid-file>] [--no-pid]\n"\
 "                [-m append|replace|forward|discard]\n" \
 "                [-i interface0 [ ... -i interfaceN]\n" \
-"                server0 [ ... serverN]\n\n"
+"                server0 [ ... serverN]\n\n" DHCRELAY_OPTION82_USAGE
 #endif
 
 static void usage() {
@@ -287,6 +300,15 @@
 			local_family_set = 1;
 			local_family = AF_INET;
 #endif
+			if (++i == argc)
+				usage();
+
+			if (argv[i] != NULL && argv[i][0] != '-')
+				agent_circuit_id_fmt = argv[i++];
+
+			if (argv[i] != NULL && argv[i][0] != '-')
+				agent_remote_id_fmt = argv[i];
+
 			add_agent_options = 1;
 		} else if (!strcmp(argv[i], "-A")) {
 #ifdef DHCPv6
@@ -937,6 +959,166 @@
 	return (-1);
 }
 
+static int
+_bridgefdbquery(const char *hwAddr, char *interface, int *vlanid) {
+
+#define xstr(s) str(s)
+#define str(s) #s
+#define FDB_STRING_LEN  100
+#define FDB_BUFFER_LEN  (FDB_STRING_LEN + 1)
+
+/*
+ * Format for sscanf() to read the 1st, 3th, and 5th
+ * space-delimited fields
+ *
+ * bridge fdb show output
+ * 6c:64:1a:00:06:13 dev swp35 vlan 0 master bridge permanent
+ */
+#define FDB_LINE_FORMAT "%" xstr(FDB_STRING_LEN) "s %*s " \
+						 "%" xstr(FDB_STRING_LEN) "s %*s %d %*s"
+
+	char cmdstr[FDB_BUFFER_LEN];
+	char buf[FDB_BUFFER_LEN];
+	char macAddr[FDB_BUFFER_LEN];
+
+	if ((interface == NULL) || (vlanid == NULL)) {
+		return 0;
+	}
+	sprintf(cmdstr, "bridge fdb show | grep -m 1 %s", hwAddr);
+	FILE *cmd = popen(cmdstr, "r");
+
+	if (cmd != NULL) {
+		while (fgets(buf, sizeof(buf), cmd)) {
+			sscanf(buf, FDB_LINE_FORMAT, macAddr, interface, vlanid);
+			log_debug ("bridgefdbquery: macAddr:%s interface: %s vlanid %d",
+					   macAddr,
+					   interface, *vlanid);
+		}
+		pclose(cmd);
+		return 0;
+	}
+
+	return -1;
+}
+
+/*
+ * Format the message that will be used by circuit_id and remote_id
+ */
+static int
+format_relay_agent_rfc3046_msg(struct interface_info *ip, struct dhcp_packet *packet,
+								const char *format, char *msg, size_t msgn) {
+	size_t len = 0;
+	char hostname[HOST_NAME_MAX + 1] = { 0 };
+	char ifname[IFNAMSIZ + 1] = { 0 };
+	char *buf = msg;
+
+	for ( ; format && *format && len < msgn; ++format) {
+		size_t strn = 0;
+		const char *str = NULL;
+
+		if (*format == '%') {
+			switch (*++format) {
+				case '\0':
+					--format;
+				break;
+
+				case '%':  /* A literal '%' */
+					str = "%";
+				break;
+
+				case 'h': /* Hostname */
+					gethostname(hostname, HOST_NAME_MAX);
+					str = hostname;
+				break;
+
+				case 'p':  /* Name of interface that we received the request from */
+					/*
+					* Query FDB to identify the exact physical interface only when source MAC address 
+					* is present and '20: DHCP relay agent IP address' (giaddr) is not present
+					*/
+					if (packet->htype && !packet->giaddr.s_addr) {
+						int ret = 0, vlanid = 0;
+
+						ret = _bridgefdbquery(print_hw_addr(packet->htype, packet->hlen, packet->chaddr),
+											  ip->name,
+											  &vlanid);
+
+						if (ret < 0) {
+							log_debug("MAC Address: %s (interface:%s vlan:%d) not found in bridge fdb show",
+									  print_hw_addr (packet->htype, packet->hlen, packet->chaddr),
+									  ip->name,
+									  vlanid);
+							strncpy(ifname, ip->name, IFNAMSIZ);
+						}
+						else if (strlen(ip->name) > 0) {
+							char cmdstr[256] = { 0 };
+							char cmdout[256] = { 0 };
+
+							log_debug("Adding option 82 interface name for MAC Address: %s as %s",
+									  print_hw_addr (packet->htype, packet->hlen, packet->chaddr),
+									  ip->name);
+
+						// Translate SONiC interface name to vendor alias
+						sprintf(cmdstr, "sonic-cfggen -m /etc/sonic/minigraph.xml -v \"minigraph_ports['%s'].alias\"", ip->name);
+
+						FILE *cmd = popen(cmdstr, "r");
+
+						if (cmd != NULL) {
+							while (fgets(cmdout, sizeof(cmdout), cmd)) {
+								// Strip any trailing newline
+								if (cmdout[strlen(cmdout) - 1] == '\n')
+									cmdout[strlen(cmdout) - 1] = '\0';
+
+								log_debug ("Retrieved alias %s for interface %s", buf, ip->name);
+							}
+
+							pclose(cmd);
+						}
+
+						strncpy(ifname, cmdout, IFNAMSIZ);
+					}
+
+					str = ifname;
+				}
+				break;
+
+				case 'P': /* Physical address of interface that we received the request from */
+					str = print_hw_addr(ip->hw_address.hbuf[0], ip->hw_address.hlen - 1, &ip->hw_address.hbuf[1]);
+				break;
+
+				case 'C': /* 24: Client hardware address  */
+					str = print_hw_addr(packet->htype, packet->hlen, packet->chaddr);
+				break;
+
+				case 'I': /* 20: DHCP relay agent IP address */
+					str = inet_ntoa(packet->giaddr);
+				break;
+
+				default:
+					log_error("Option %%%c is unrecognized and will not be formatted!", *format);
+					continue;
+			}
+
+			if (str)
+				strn = strlen(str);
+		} else {
+			str = format;
+			strn += 1;
+		}
+
+		// Do we have room?
+		if ((strn+len) > msgn) {
+			return 0;
+		}
+
+		memcpy(buf+len, str, strn);
+		len += strn;
+	}
+
+	return len;
+}
+
+
 /*
  * Examine a packet to see if it's a candidate to have a Relay
  * Agent Information option tacked onto its tail.   If it is, tack
@@ -948,6 +1130,8 @@
 	int is_dhcp = 0, mms;
 	unsigned optlen;
 	u_int8_t *op, *nextop, *sp, *max, *end_pad = NULL;
+	char circuit_id_buf[255] = { '\0', };
+	char remote_id_buf[255] = { '\0', };
 
 	/* If we're not adding agent options to packets, we can skip
 	   this. */
@@ -1077,6 +1261,38 @@
 	op = sp;
 #endif
 
+	/* option82: custom string for circuit_id */
+	if (agent_circuit_id_fmt) {
+		size_t len = 0;
+
+		len = format_relay_agent_rfc3046_msg(ip, packet, agent_circuit_id_fmt,
+											 circuit_id_buf, sizeof(circuit_id_buf));
+
+		if (len > 0) {
+			ip->circuit_id = (uint8_t *)circuit_id_buf;
+			ip->circuit_id_len = len;
+
+			log_debug("sending on %s option82:circuit_id='%s'(%d)",
+					  ip->name, (char *)ip->circuit_id, ip->circuit_id_len);
+		}
+	}
+
+	/* option82: custom string for remote_id */
+	if (agent_remote_id_fmt) {
+		size_t len = 0;
+
+		len = format_relay_agent_rfc3046_msg(ip, packet, agent_remote_id_fmt,
+											 remote_id_buf, sizeof(remote_id_buf));
+
+		if (len > 0) {
+			ip->remote_id = (uint8_t *)remote_id_buf;
+			ip->remote_id_len = len;
+
+			log_debug("sending on %s option82:remote_id='%s'(%d)",
+					  ip->name, (char *)ip->remote_id, ip->remote_id_len);
+		}
+	}
+
 	/* Sanity check.  Had better not ever happen. */
 	if ((ip->circuit_id_len > 255) ||(ip->circuit_id_len < 1))
 		log_fatal("Circuit ID length %d out of range [1-255] on "