From d90f47ef9c76fd76a74d38558a106a2ea202060f Mon Sep 17 00:00:00 2001
From: Urs Thuermann <urs.thuermann@volkswagen.de>
Date: Fri, 6 Jul 2007 15:50:55 +0000
Subject: [PATCH] Add a tool "vcan" to add/remove vcan interfaces.

---
 vcan.c | 142 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 142 insertions(+)
 create mode 100644 vcan.c

diff --git a/vcan.c b/vcan.c
new file mode 100644
index 0000000..1539458
--- /dev/null
+++ b/vcan.c
@@ -0,0 +1,142 @@
+/*
+ * a real quick'n'dirty hack to add/remove vcan interfaces.
+ * (also to have something to test the new RTNL API in vcan.)
+ * this will be added to ip(8) of the iproute package, making
+ * this hack obsolete.
+ * 
+ * we don't check the return value of sendto() and don't wait for
+ * a reply using recvmsg().  We just hope everything works fine,
+ * otherwise use strace, or feel free to add the code before this
+ * whole thing is dumped to the bit bucket.
+ *
+ * urs
+ */
+
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <sys/socket.h>
+#include <net/if.h>
+
+#include <asm/types.h>
+#include <linux/netlink.h>
+#include <linux/rtnetlink.h>
+
+//#include <linux/if_link.h>
+
+#define IFLA_LINKINFO 18
+
+enum
+{
+    IFLA_INFO_UNSPEC,
+    IFLA_INFO_NAME,
+    IFLA_INFO_DATA,
+    IFLA_INFO_XSTATS,
+    __IFLA_INFO_MAX,
+};
+
+#define NLMSG_TAIL(nmsg) \
+        ((struct rtattr *)(((void *) (nmsg)) + NLMSG_ALIGN((nmsg)->nlmsg_len)))
+
+int addattr_l(struct nlmsghdr *n, int maxlen, int type, const void *data,
+	      int alen);
+
+void usage()
+{
+    fprintf(stderr, "Usage: vcan create\n"
+		    "       vcan delete iface\n");
+    exit(1);
+}
+
+int main(int argc, char **argv)
+{
+    int s;
+    char *cmd, *dev;
+    struct {
+	struct nlmsghdr  n;
+	struct ifinfomsg i;
+	char             buf[1024];
+    } req;
+    struct sockaddr_nl nladdr;
+    struct rtattr *linkinfo;
+    int i;
+
+#ifdef OBSOLETE
+    fprintf(stderr, "This program is a temporary hack and is now obsolete.\n"
+	    "Please use ip(8) instead, i.e.\n"
+	    "    ip link add type vcan       or\n"
+	    "    ip link delete iface\n");
+    exit(1);
+#endif
+    if (argc < 2)
+	usage();
+    cmd = argv[1];
+
+    s = socket(PF_NETLINK, SOCK_RAW, NETLINK_ROUTE);
+
+    memset(&req, 0, sizeof(req));
+
+    if (strcmp(cmd, "create") == 0) {
+	req.n.nlmsg_len   = NLMSG_LENGTH(sizeof(struct ifinfomsg));
+	req.n.nlmsg_flags = NLM_F_REQUEST | NLM_F_CREATE | NLM_F_EXCL;
+	req.n.nlmsg_type  = RTM_NEWLINK;
+	req.n.nlmsg_seq   = 0;
+	req.i.ifi_family  = AF_UNSPEC;
+
+	linkinfo = NLMSG_TAIL(&req.n);
+	addattr_l(&req.n, sizeof(req), IFLA_LINKINFO, NULL, 0);
+	addattr_l(&req.n, sizeof(req), IFLA_INFO_NAME, "vcan", strlen("vcan"));
+	linkinfo->rta_len = (void*)NLMSG_TAIL(&req.n) - (void*)linkinfo;
+
+    } else if (strcmp(cmd, "delete") == 0) {
+	if (argc < 3)
+	    usage();
+	dev = argv[2];
+	req.n.nlmsg_len   = NLMSG_LENGTH(sizeof(struct ifinfomsg));
+	req.n.nlmsg_flags = NLM_F_REQUEST;
+	req.n.nlmsg_type  = RTM_DELLINK;
+	req.i.ifi_family  = AF_UNSPEC;
+	req.i.ifi_index   = if_nametoindex(dev);
+    } else
+	usage();
+
+    memset(&nladdr, 0, sizeof(nladdr));
+    nladdr.nl_family = AF_NETLINK;
+    nladdr.nl_pid    = 0;
+    nladdr.nl_groups = 0;
+#if 1
+    sendto(s, &req, req.n.nlmsg_len, 0,
+	   (struct sockaddr*)&nladdr, sizeof(nladdr));
+#else
+    for (i = 0; i < req.n.nlmsg_len; i++) {
+	printf(" %02x", ((unsigned char*)&req)[i]);
+	if (i % 16 == 15)
+	    putchar('\n');
+    }
+    putchar('\n');
+#endif
+    close(s);
+
+    return 0;
+}
+
+int addattr_l(struct nlmsghdr *n, int maxlen, int type, const void *data,
+	      int alen)
+{
+    int len = RTA_LENGTH(alen);
+    struct rtattr *rta;
+
+    if (NLMSG_ALIGN(n->nlmsg_len) + RTA_ALIGN(len) > maxlen) {
+	fprintf(stderr, "addattr_l ERROR: message exceeded bound of %d\n",
+		maxlen);
+	return -1;
+    }
+    rta = NLMSG_TAIL(n);
+    rta->rta_type = type;
+    rta->rta_len = len;
+    memcpy(RTA_DATA(rta), data, alen);
+    n->nlmsg_len = NLMSG_ALIGN(n->nlmsg_len) + RTA_ALIGN(len);
+    return 0;
+}
-- 
2.39.2