vpnkit: Add a few files from vpnkit

From:
    https://github.com/moby/vpnkit
    commit 2ffc1dd8a84ea7359dd09b1f4b51bb728d4f46a0
    c/vpnkit-tap-vsockd/protocol.h
    c/vpnkit-tap-vsockd/protocol.c

arch/sim/src/sim/vpnkit/protocol.c

@@ -0,0 +1,224 @@
+#include <sys/socket.h>
+#include <sys/types.h>
+#include <sys/uio.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <string.h>
+#include <stdio.h>
+
+#include "log.h"
+#include "protocol.h"
+
+/* Version 0 of the protocol used this */
+char expected_hello_old[5] = {'V', 'M', 'N', 'E', 'T'};
+
+/* Version 1 and later of the protocol used this */
+char expected_hello[5] = {'V', 'M', 'N', '3', 'T'};
+
+int really_read(int fd, uint8_t *buffer, size_t total)
+{
+	size_t remaining = total;
+	ssize_t n;
+
+	while (remaining > 0) {
+		n = read(fd, buffer, remaining);
+		if (n == 0) {
+			ERROR("EOF reading from socket: closing\n");
+			goto err;
+		}
+		if (n < 0) {
+			ERROR(
+				"Failure reading from socket: closing: %s",
+			    strerror(errno));
+			goto err;
+		}
+		remaining -= (size_t) n;
+		buffer = buffer + n;
+	}
+	return 0;
+err:
+	/*
+	 * On error: stop reading from the socket and trigger a clean
+	 * shutdown
+	 */
+	shutdown(fd, SHUT_RD);
+	return -1;
+}
+
+int really_write(int fd, uint8_t *buffer, size_t total)
+{
+	size_t remaining = total;
+	ssize_t n;
+
+	while (remaining > 0) {
+		n = write(fd, buffer, remaining);
+		if (n == 0) {
+			ERROR("EOF writing to socket: closing");
+			goto err;
+		}
+		if (n < 0) {
+			ERROR(
+				"Failure writing to socket: closing: %s",
+			    strerror(errno));
+			goto err;
+		}
+		remaining -= (size_t) n;
+		buffer = buffer + n;
+	}
+	return 0;
+err:
+	/* On error: stop listening to the socket */
+	shutdown(fd, SHUT_WR);
+	return -1;
+}
+
+struct init_message *create_init_message()
+{
+	struct init_message *m;
+
+	m = malloc(sizeof(struct init_message));
+	if (!m)
+		return NULL;
+
+	bzero(m, sizeof(struct init_message));
+	memcpy(&m->hello[0], &expected_hello[0], sizeof(m->hello));
+	m->version = CURRENT_VERSION;
+	memset(&m->commit[0], 0, sizeof(m->commit));
+
+	return m;
+}
+
+char *print_init_message(struct init_message *m)
+{
+	char tmp[41];
+
+	memcpy(&tmp[0], &m->commit[0], 40);
+	tmp[40] = '\000';
+	char *buffer;
+	int n;
+
+	buffer = malloc(80);
+	if (!buffer)
+		return NULL;
+
+	n = snprintf(buffer, 80, "version %d, commit %s", m->version, tmp);
+	if (n < 0) {
+		perror("Failed to format init_message");
+		exit(1);
+	}
+	return buffer;
+}
+
+int read_init_message(int fd, struct init_message *ci)
+{
+	int res;
+
+	bzero(ci, sizeof(struct init_message));
+
+	res = really_read(fd, (uint8_t *)&ci->hello[0], sizeof(ci->hello));
+	if (res  == -1) {
+		ERROR("Failed to read hello from client");
+		return -1;
+	}
+
+	res = memcmp(&ci->hello[0],
+		     &expected_hello_old[0], sizeof(expected_hello_old));
+	if (res == 0) {
+		ci->version = 0;
+		return 0;
+	}
+
+	res = memcmp(&ci->hello[0],
+		     &expected_hello[0], sizeof(expected_hello));
+	if (res != 0) {
+		ERROR("Failed to read header magic from client");
+		return -1;
+	}
+
+	res = really_read(fd, (uint8_t *)&ci->version, sizeof(ci->version));
+	if (res == -1) {
+		ERROR("Failed to read header version from client");
+		return -1;
+	}
+
+	res = really_read(fd, (uint8_t *)&ci->commit[0], sizeof(ci->commit));
+	if (res == -1) {
+		ERROR("Failed to read header hash from client");
+		return -1;
+	}
+
+	return 0;
+}
+
+int write_init_message(int fd, struct init_message *ci)
+{
+	int res;
+
+	res = really_write(fd, (uint8_t *)&ci->hello[0], sizeof(ci->hello));
+	if (res == -1) {
+		ERROR("Failed to write hello to client");
+		return -1;
+	}
+	if (ci->version > 0) {
+		res = really_write(fd, (uint8_t *)&ci->version,
+				   sizeof(ci->version));
+		if (res == -1) {
+			ERROR("Failed to write version to client");
+			return -1;
+		}
+		res = really_write(fd, (uint8_t *)&ci->commit[0],
+				   sizeof(ci->commit));
+		if (res == -1) {
+			ERROR("Failed to write header hash to client");
+			return -1;
+		}
+	}
+	return 0;
+}
+
+int read_vif_response(int fd, struct vif_info *vif)
+{
+	struct msg_response msg;
+
+	if (really_read(fd, (uint8_t*)&msg, sizeof(msg)) == -1) {
+		ERROR("Client failed to read server response");
+		return -1;
+	}
+
+	switch (msg.response_type) {
+		case rt_vif:
+			memcpy((uint8_t*)vif, (uint8_t*)&msg.vif, sizeof(*vif));
+			return 0;
+		case rt_disconnect:
+			ERROR("Server disconnected: %*s", msg.disconnect.len, msg.disconnect.msg);
+			return -1;
+		default:
+			ERROR("Unknown response type from server");
+			return -1;
+	}
+
+}
+
+int write_command(int fd, enum command *c)
+{
+	uint8_t command = *c;
+
+	if (really_write(fd, (uint8_t *)&command, sizeof(command)) == -1) {
+		ERROR("Failed to write command to client");
+		return -1;
+	}
+	return 0;
+}
+
+int write_ethernet_args(int fd, struct ethernet_args *args)
+{
+    uint8_t buffer[40];
+    memset(&buffer[0], 0, sizeof(buffer));
+    memcpy(&buffer[0], (uint8_t *)&args->uuid_string[0], 36);
+
+	if (really_write(fd, (uint8_t *)&buffer, sizeof(buffer)) == -1) {
+		ERROR("Failed to write ethernet args to client");
+		return -1;
+	}
+	return 0;
+}

arch/sim/src/sim/vpnkit/protocol.h

@@ -0,0 +1,77 @@
+#ifndef _VMNET_PROTOCOL_H_
+#define _VMNET_PROTOCOL_H_
+
+#include <errno.h>
+#include <stdint.h>
+
+/* Client -> Server init_message */
+/* Server -> Client init_message */
+struct init_message {
+	char hello[5];
+	uint8_t _padding[3];
+	uint32_t version;
+	char commit[40]; /* git sha of the compiled commit */
+};
+
+/*
+ * This should be bumped whenever we add something (like a feature or a
+ * bugfix) and we wish the UI to be able to detect when to trigger a
+ * reinstall.
+ */
+#define CURRENT_VERSION 22
+
+extern struct init_message *create_init_message(void);
+extern int read_init_message(int fd, struct init_message *ci);
+extern int write_init_message(int fd, struct init_message *ci);
+extern char *print_init_message(struct init_message *m);
+
+/* Client -> Server command */
+enum command {
+	ethernet = 1,
+};
+
+/* Server -> Client response */
+enum response_type {
+    rt_vif = 1,
+    rt_disconnect = 2,
+};
+
+extern int write_command(int fd, enum command *c);
+
+/* Client -> Server command arguments */
+struct ethernet_args {
+	char uuid_string[36];
+};
+
+extern int write_ethernet_args(int fd, struct ethernet_args *args);
+
+/* Server -> Client: details of a vif */
+struct vif_info {
+	uint16_t mtu;
+	uint16_t max_packet_size;
+	uint8_t mac[6];
+} __attribute__((packed));
+
+/* Server -> Client: disconnect w/reason */
+struct disconnect_reason {
+    uint8_t len;
+    char msg[256];
+} __attribute__((packed));
+
+struct msg_response {
+    uint8_t response_type;
+    union {
+        struct vif_info vif;
+        struct disconnect_reason disconnect;
+    };
+} __attribute__((packed));
+
+extern int read_vif_response(int fd, struct vif_info *vif);
+
+extern char expected_hello[5];
+extern char expected_hello_old[5];
+
+extern int really_read(int fd, uint8_t *buffer, size_t total);
+extern int really_write(int fd, uint8_t *buffer, size_t total);
+
+#endif /* _VMNET_PROTOCOL_H_ */