nhrpd: implement next hop resolution protocol

This provides DMVPN support and integrates to strongSwan. Please read
README.nhrpd and README.kernel for more details.

[DL: cherry-picked from dafa05e65fe4b3b3ed5525443f554215ba14f42c]
[DL: merge partially resolved, this commit will not build.]
Signed-off-by: Timo Teräs <timo.teras@iki.fi>
Signed-off-by: David Lamparter <equinox@opensourcerouting.org>

1 files changed, 153 insertions, 0 deletions

diff --git a/nhrpd/linux.c b/nhrpd/linux.c
new file mode 100644
index 000000000..1e9c69eb8
--- /dev/null
+++ b/nhrpd/linux.c
@@ -0,0 +1,153 @@
+/* NHRP daemon Linux specific glue
+ * Copyright (c) 2014-2015 Timo Teräs
+ *
+ * This file is free software: you may copy, redistribute and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 2 of the License, or
+ * (at your option) any later version.
+ */
+
+#include <fcntl.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <string.h>
+#include <sys/ioctl.h>
+#include <sys/socket.h>
+#include <sys/types.h>
+#include <asm/types.h>
+#include <arpa/inet.h>
+#include <linux/netlink.h>
+#include <linux/rtnetlink.h>
+#include <linux/ip.h>
+#include <linux/if_arp.h>
+#include <linux/if_tunnel.h>
+
+#include "nhrp_protocol.h"
+#include "os.h"
+#include "netlink.h"
+
+static int nhrp_socket_fd = -1;
+
+int os_socket(void)
+{
+	if (nhrp_socket_fd < 0)
+		nhrp_socket_fd = socket(PF_PACKET, SOCK_DGRAM, htons(ETH_P_NHRP));
+	return nhrp_socket_fd;
+}
+
+int os_sendmsg(const uint8_t *buf, size_t len, int ifindex, const uint8_t *addr, size_t addrlen)
+{
+	struct sockaddr_ll lladdr;
+	struct iovec iov = {
+		.iov_base = (void*) buf,
+		.iov_len = len,
+	};
+	struct msghdr msg = {
+		.msg_name = &lladdr,
+		.msg_namelen = sizeof(lladdr),
+		.msg_iov = &iov,
+		.msg_iovlen = 1,
+	};
+	int status;
+
+	if (addrlen > sizeof(lladdr.sll_addr))
+		return -1;
+
+	memset(&lladdr, 0, sizeof(lladdr));
+	lladdr.sll_family = AF_PACKET;
+	lladdr.sll_protocol = htons(ETH_P_NHRP);
+	lladdr.sll_ifindex = ifindex;
+	lladdr.sll_halen = addrlen;
+	memcpy(lladdr.sll_addr, addr, addrlen);
+
+	status = sendmsg(nhrp_socket_fd, &msg, 0);
+	if (status < 0)
+		return -1;
+
+	return 0;
+}
+
+int os_recvmsg(uint8_t *buf, size_t *len, int *ifindex, uint8_t *addr, size_t *addrlen)
+{
+	struct sockaddr_ll lladdr;
+	struct iovec iov = {
+		.iov_base = buf,
+		.iov_len = *len,
+	};
+	struct msghdr msg = {
+		.msg_name = &lladdr,
+		.msg_namelen = sizeof(lladdr),
+		.msg_iov = &iov,
+		.msg_iovlen = 1,
+	};
+	int r;
+
+	r = recvmsg(nhrp_socket_fd, &msg, MSG_DONTWAIT);
+	if (r < 0)
+		return r;
+
+	*len = r;
+	*ifindex = lladdr.sll_ifindex;
+
+	if (*addrlen <= (size_t) lladdr.sll_addr) {
+		if (memcmp(lladdr.sll_addr, "\x00\x00\x00\x00", 4) != 0) {
+			memcpy(addr, lladdr.sll_addr, lladdr.sll_halen);
+			*addrlen = lladdr.sll_halen;
+		} else {
+			*addrlen = 0;
+		}
+	}
+
+	return 0;
+}
+
+static int linux_configure_arp(const char *iface, int on)
+{
+	struct ifreq ifr;
+
+	strncpy(ifr.ifr_name, iface, IFNAMSIZ);
+	if (ioctl(nhrp_socket_fd, SIOCGIFFLAGS, &ifr))
+		return -1;
+
+	if (on)
+		ifr.ifr_flags &= ~IFF_NOARP;
+	else
+		ifr.ifr_flags |= IFF_NOARP;
+
+	if (ioctl(nhrp_socket_fd, SIOCSIFFLAGS, &ifr))
+		return -1;
+
+	return 0;
+}
+
+static int linux_icmp_redirect_off(const char *iface)
+{
+	char fname[256];
+	int fd, ret = -1;
+
+	sprintf(fname, "/proc/sys/net/ipv4/conf/%s/send_redirects", iface);
+	fd = open(fname, O_WRONLY);
+	if (fd < 0)
+		return -1;
+	if (write(fd, "0\n", 2) == 2)
+		ret = 0;
+	close(fd);
+
+	return ret;
+}
+
+int os_configure_dmvpn(unsigned int ifindex, const char *ifname, int af)
+{
+	int ret = -1;
+
+	switch (af) {
+	case AF_INET:
+		ret  = linux_icmp_redirect_off("all");
+		ret |= linux_icmp_redirect_off(ifname);
+		ret |= netlink_configure_arp(ifindex, AF_INET);
+		ret |= linux_configure_arp(ifname, 1);
+		break;
+	}
+
+	return ret;
+}