nlsock.c

#include <errno.h>
#include <string.h>
#include <unistd.h>

#include <sys/types.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <linux/netlink.h>

#include "util.h"
#include "diskev.h"

#define NL_SOCKET_BUFSZ		32768

int nlsock_open(int subscribe)
{
	int sndbuf = NL_SOCKET_BUFSZ;
	int rcvbuf = NL_SOCKET_BUFSZ;
	int nlsock;
	struct sockaddr_nl addr;
	socklen_t addrlen;

	nlsock = socket(AF_NETLINK, SOCK_RAW, NETLINK_KOBJECT_UEVENT);
	if (nlsock < 0)
		die("socket(AF_NETLINK) failed");

	vdebug("Opened netlink socket %u, subscribe %i", nlsock, subscribe);

	set_nio(nlsock);
	set_coe(nlsock);

	if (setsockopt(nlsock, SOL_SOCKET, SO_SNDBUF,
		       &sndbuf, sizeof(sndbuf)) < 0)
		die("setsockopt(SO_SNDBUF) failed");

	if (setsockopt(nlsock, SOL_SOCKET, SO_RCVBUF,
		       &rcvbuf, sizeof(rcvbuf)) < 0)
		die("setsockopt(SO_RCVBUF) failed");

	addrlen = sizeof(addr);
	memset(&addr, 0, addrlen);

	addr.nl_family = AF_NETLINK;
	addr.nl_groups = subscribe;

	if (bind(nlsock, (struct sockaddr*)&addr, addrlen)) {
		die("bind() failed ion netlink socket");
	}

	if (getsockname(nlsock, (struct sockaddr*) &addr, &addrlen) < 0)
		die("getsockname() failed");

	if (addrlen != sizeof(addr) ||
	    addr.nl_family != AF_NETLINK)
		die("whatever ...");

	return nlsock;
}

void nlsock_close(int sock)
{
	close(sock);
	vdebug("Closed netlink socket %u", sock);
}

int nlsock_recv(int sock, char *buf, size_t len)
{
	int size;	/* received reply length */
	struct sockaddr_nl nladdr;
	struct iovec iov;
	struct msghdr msg = {
		.msg_name = &nladdr,
		.msg_namelen = sizeof(nladdr),
		.msg_iov = &iov,
		.msg_iovlen = 1,
	};

	do {
		iov.iov_len = len;
		iov.iov_base = buf;
		size = recvmsg(sock, &msg, 0);
	} while (size < 0 && (errno == EINTR  || errno == ENOBUFS));
	// ENOBUFS is raised when NL socket buffer is full

	if (size < 0) {
		if (errno == EAGAIN)
			return 0;
		verror("failed receive on socket %i, err: %s (%i)\n",
		      sock, strerror(errno), errno);
		return -1;
	} else if (size == 0) {
		vdebug("empty responce on socket %i, closing\n", sock);
		close(sock);
		return 0;
	}

	// FIXME(edzius): This could cause NL events caching,
	// depending on FD poll method used. E.g. when used
	// with edge triggered poll it could lead to caching.
	if (msg.msg_flags & (MSG_TRUNC | MSG_CTRUNC)) {
		warn("truncated message (%x), discard", msg.msg_flags);
		return 0;
	}

	return size;
}

static int nlev_update_part(struct diskev *evt, char *line)
{
	char *pos;

	vdebug("Processing ENV line: '%s'", line);

	pos = strchr(line, '=');
	if (!pos) {
		vwarn("Anomalous EVN parameter: '%s'", line);
		return -1;
	}
	*pos = '\0';
	pos++;

	if (!strcmp(line, "ACTION")) {
		evt->action = strdup(pos);
	} else if (!strcmp(line, "SUBSYSTEM")) {
		evt->subsys = strdup(pos);
	} else if (!strcmp(line, "DEVTYPE")) {
		evt->type = strdup(pos);
	} else if (!strcmp(line, "DEVNAME")) {
		if (strncmp(pos, "/dev", 4))
			evt->device = strfdup("/dev/%s", pos);
		else
			evt->device = strdup(pos);
	} else if (!strcmp(line, "ID_FS_TYPE")) {
		evt->filesys = strdup(pos);
	} else if (!strcmp(line, "ID_SERIAL_SHORT")) {
		evt->serial = strdup(pos);
	} else if (!strcmp(line, "ID_FS_LABEL")) {
		evt->label = strdup(pos);
	} else if (!strcmp(line, "ID_FS_UUID")) {
		evt->fsuuid = strdup(pos);
	} else if (!strcmp(line, "ID_PART_ENTRY_UUID")) {
		evt->partuuid = strdup(pos);
	} else {
		return 1;
	}

	vinfo("Included ENV param: '%s' = '%s'", line, pos);

	return 0;
}

int nlev_parse(struct diskev *evt, char *data, int size)
{
	char *cur, *end;
	int cnt;
	int prc = 0;

	memset(evt, 0, sizeof(*evt));

	cur = data;
	end = data + size;
	while (cur < end) {
		cnt = strlen(cur);
		if (cnt <= 0)
			break;

		nlev_update_part(evt, cur);
		cur += cnt + 1;
		prc += cnt + 1;
		vdebug("Processed NL param, size %u, progress %u/%u", cnt, prc, size);
	}

	if (ev_check(evt)) {
		vinfo("Incorrect event type %s/%s/%s", evt->subsys, evt->type, evt->device);
		ev_free(evt);
		return 1;
	}

	if (ev_validate(evt)) {
		verror("Invalid event parameters, device %s, size %u", evt->device, size);
		ev_free(evt);
		return 1;
	}

	vinfo("Processed event, size %u", size);

	return 0;
}