merd: ARP and DHCP handlers, connection tracking fixes

With this, merd provides a fully functional IPv4 environment to
guests, requiring a single capability, CAP_NET_RAW.

Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

1 files changed, 47 insertions, 0 deletions

diff --git a/merd.h b/merd.h
new file mode 100644
index 0000000..78e3c0b
--- /dev/null
+++ b/merd.h
@@ -0,0 +1,47 @@
+#define CT_SIZE		4096
+#define UNIX_SOCK_PATH	"/tmp/merd.socket"
+
+/**
+ * struct ct4 - IPv4 connection tracking entry
+ * @p:		IANA protocol number
+ * @sa:		Source address (as seen from tap interface)
+ * @da:		Destination address
+ * @sp:		Source port, network order
+ * @dp:		Destination port, network order
+ * @hd:		Destination MAC address
+ * @hs:		Source MAC address
+ * @fd:		File descriptor for corresponding AF_INET socket
+ */
+struct ct4 {
+	uint8_t p;
+	uint32_t sa;
+	uint32_t da;
+	uint16_t sp;
+	uint16_t dp;
+	unsigned char hd[ETH_ALEN];
+	unsigned char hs[ETH_ALEN];
+	int fd;
+};
+
+/**
+ * struct ctx - Execution context
+ * @epollfd:	file descriptor for epoll instance
+ * @fd_unix:	AF_UNIX socket for tap file descriptor
+ * @map4:	Connection tracking table
+ * @addr4:	IPv4 address for external, routable interface
+ * @mask4:	IPv4 netmask, network order
+ * @gw4:	Default IPv4 gateway, network order
+ * @dns4:	IPv4 DNS address, network order
+ * @ifn:	Name of routable interface
+ */
+struct ctx {
+	int epollfd;
+	int fd_unix;
+	struct ct4 map4[CT_SIZE];
+	unsigned char mac[ETH_ALEN];
+	unsigned long addr4;
+	unsigned long mask4;
+	unsigned long gw4;
+	unsigned long dns4;
+	char ifn[IF_NAMESIZE];
+};