networkd: add basic LLDP transmission support

Let's add some minimalistic LLDP sender support. The idea is that this is
either on or off, and all fields determined automatically rather than
configured explicitly.

diff --git a/src/network/networkd-lldp-tx.c b/src/network/networkd-lldp-tx.c
new file mode 100644 (file)
index 0000000..184152d
--- /dev/null
+++ b/src/network/networkd-lldp-tx.c
@@ -0,0 +1,347 @@
+/***
+  This file is part of elogind.
+
+  Copyright 2016 Lennart Poettering
+
+  elogind is free software; you can redistribute it and/or modify it
+  under the terms of the GNU Lesser General Public License as published by
+  the Free Software Foundation; either version 2.1 of the License, or
+  (at your option) any later version.
+
+  elogind is distributed in the hope that it will be useful, but
+  WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+  Lesser General Public License for more details.
+
+  You should have received a copy of the GNU Lesser General Public License
+  along with elogind; If not, see <http://www.gnu.org/licenses/>.
+***/
+
+#include <endian.h>
+#include <inttypes.h>
+#include <string.h>
+
+#include "fd-util.h"
+#include "fileio.h"
+#include "hostname-util.h"
+#include "lldp.h"
+#include "networkd-lldp-tx.h"
+#include "random-util.h"
+#include "socket-util.h"
+#include "string-util.h"
+#include "unaligned.h"
+
+/* The LLDP spec calls this "txFastInit", see 9.2.5.19 */
+#define LLDP_TX_FAST_INIT 4U
+
+/* The LLDP spec calls this "msgTxHold", see 9.2.5.6 */
+#define LLDP_TX_HOLD 4U
+
+/* The jitter range to add, see 9.2.2. */
+#define LLDP_JITTER_USEC (400U * USEC_PER_MSEC)
+
+/* The LLDP spec calls this msgTxInterval, but we subtract half the jitter off it. */
+#define LLDP_TX_INTERVAL_USEC (30U * USEC_PER_SEC - LLDP_JITTER_USEC / 2)
+
+/* The LLDP spec calls this msgFastTx, but we subtract half the jitter off it. */
+#define LLDP_FAST_TX_USEC (1U * USEC_PER_SEC - LLDP_JITTER_USEC / 2)
+
+static int lldp_write_tlv_header(uint8_t **p, uint8_t id, size_t sz) {
+        assert(p);
+
+        if (id > 127)
+                return -EBADMSG;
+        if (sz > 511)
+                return -ENOBUFS;
+
+        (*p)[0] = (id << 1) | !!(sz & 256);
+        (*p)[1] = sz & 255;
+
+        *p = *p + 2;
+        return 0;
+}
+
+static int lldp_make_packet(
+                const struct ether_addr *hwaddr,
+                const char *machine_id,
+                const char *ifname,
+                uint16_t ttl,
+                const char *port_description,
+                const char *hostname,
+                const char *pretty_hostname,
+                uint16_t system_capabilities,
+                uint16_t enabled_capabilities,
+                void **ret, size_t *sz) {
+
+        size_t machine_id_length, ifname_length, port_description_length = 0, hostname_length = 0, pretty_hostname_length = 0;
+        _cleanup_free_ void *packet = NULL;
+        struct ether_header *h;
+        uint8_t *p;
+        size_t l;
+        int r;
+
+        assert(hwaddr);
+        assert(machine_id);
+        assert(ifname);
+        assert(ret);
+        assert(sz);
+
+        machine_id_length = strlen(machine_id);
+        ifname_length = strlen(ifname);
+
+        if (port_description)
+                port_description_length = strlen(port_description);
+
+        if (hostname)
+                hostname_length = strlen(hostname);
+
+        if (pretty_hostname)
+                pretty_hostname_length = strlen(pretty_hostname);
+
+        l = sizeof(struct ether_header) +
+                /* Chassis ID */
+                2 + 1 + machine_id_length +
+                /* Port ID */
+                2 + 1 + ifname_length +
+                /* TTL */
+                2 + 2 +
+                /* System Capabilities */
+                2 + 4 +
+                /* End */
+                2;
+
+        /* Port Description */
+        if (port_description)
+                l += 2 + port_description_length;
+
+        /* System Name */
+        if (hostname)
+                l += 2 + hostname_length;
+
+        /* System Description */
+        if (pretty_hostname)
+                l += 2 + pretty_hostname_length;
+
+        packet = malloc(l);
+        if (!packet)
+                return -ENOMEM;
+
+        h = (struct ether_header*) packet;
+        h->ether_type = htobe16(ETHERTYPE_LLDP);
+        memcpy(h->ether_dhost, &(struct ether_addr) { LLDP_MULTICAST_ADDR }, ETH_ALEN);
+        memcpy(h->ether_shost, hwaddr, ETH_ALEN);
+
+        p = (uint8_t*) packet + sizeof(struct ether_header);
+
+        r = lldp_write_tlv_header(&p, LLDP_TYPE_CHASSIS_ID, 1 + machine_id_length);
+        if (r < 0)
+                return r;
+        *(p++) = LLDP_CHASSIS_SUBTYPE_LOCALLY_ASSIGNED;
+        p = mempcpy(p, machine_id, machine_id_length);
+
+        r = lldp_write_tlv_header(&p, LLDP_TYPE_PORT_ID, 1 + ifname_length);
+        if (r < 0)
+                return r;
+        *(p++) = LLDP_PORT_SUBTYPE_INTERFACE_NAME;
+        p = mempcpy(p, ifname, ifname_length);
+
+        r = lldp_write_tlv_header(&p, LLDP_TYPE_TTL, 2);
+        if (r < 0)
+                return r;
+        unaligned_write_be16(p, ttl);
+        p += 2;
+
+        if (port_description) {
+                r = lldp_write_tlv_header(&p, LLDP_TYPE_PORT_DESCRIPTION, port_description_length);
+                if (r < 0)
+                        return r;
+                p = mempcpy(p, port_description, port_description_length);
+        }
+
+        if (hostname) {
+                r = lldp_write_tlv_header(&p, LLDP_TYPE_SYSTEM_NAME, hostname_length);
+                if (r < 0)
+                        return r;
+                p = mempcpy(p, hostname, hostname_length);
+        }
+
+        if (pretty_hostname) {
+                r = lldp_write_tlv_header(&p, LLDP_TYPE_SYSTEM_DESCRIPTION, pretty_hostname_length);
+                if (r < 0)
+                        return r;
+                p = mempcpy(p, pretty_hostname, pretty_hostname_length);
+        }
+
+        r = lldp_write_tlv_header(&p, LLDP_TYPE_SYSTEM_CAPABILITIES, 4);
+        if (r < 0)
+                return r;
+        unaligned_write_be16(p, system_capabilities);
+        p += 2;
+        unaligned_write_be16(p, enabled_capabilities);
+        p += 2;
+
+        r = lldp_write_tlv_header(&p, LLDP_TYPE_END, 0);
+        if (r < 0)
+                return r;
+
+        assert(p == (uint8_t*) packet + l);
+
+        *ret = packet;
+        *sz = l;
+
+        packet = NULL;
+        return 0;
+}
+
+static int lldp_send_packet(int ifindex, const void *packet, size_t packet_size) {
+
+        union sockaddr_union sa = {
+                .ll.sll_family = AF_PACKET,
+                .ll.sll_protocol = htobe16(ETHERTYPE_LLDP),
+                .ll.sll_ifindex = ifindex,
+                .ll.sll_halen = ETH_ALEN,
+                .ll.sll_addr = LLDP_MULTICAST_ADDR,
+        };
+
+        _cleanup_close_ int fd = -1;
+        ssize_t l;
+
+        assert(ifindex > 0);
+        assert(packet || packet_size <= 0);
+
+        fd = socket(PF_PACKET, SOCK_RAW|SOCK_CLOEXEC, IPPROTO_RAW);
+        if (fd < 0)
+                return -errno;
+
+        l = sendto(fd, packet, packet_size, MSG_NOSIGNAL, &sa.sa, sizeof(sa.ll));
+        if (l < 0)
+                return -errno;
+
+        if ((size_t) l != packet_size)
+                return -EIO;
+
+        return 0;
+}
+
+static int link_send_lldp(Link *link) {
+        char machine_id_string[SD_ID128_STRING_MAX];
+        _cleanup_free_ char *hostname = NULL, *pretty_hostname = NULL;
+        _cleanup_free_ void *packet = NULL;
+        size_t packet_size = 0;
+        sd_id128_t machine_id;
+        uint16_t caps;
+        usec_t ttl;
+        int r;
+
+        r = sd_id128_get_machine(&machine_id);
+        if (r < 0)
+                return r;
+
+        (void) gethostname_strict(&hostname);
+        (void) parse_env_file("/etc/machine-info", NEWLINE, "PRETTY_HOSTNAME", &pretty_hostname, NULL);
+
+        ttl = DIV_ROUND_UP(LLDP_TX_INTERVAL_USEC * LLDP_TX_HOLD + 1, USEC_PER_SEC);
+        if (ttl > (usec_t) UINT16_MAX)
+                ttl = (usec_t) UINT16_MAX;
+
+        caps = (link->network && link->network->ip_forward != ADDRESS_FAMILY_NO) ?
+                LLDP_SYSTEM_CAPABILITIES_ROUTER :
+                LLDP_SYSTEM_CAPABILITIES_STATION;
+
+        r = lldp_make_packet(&link->mac,
+                             sd_id128_to_string(machine_id, machine_id_string),
+                             link->ifname,
+                             (uint16_t) ttl,
+                             link->network ? link->network->description : NULL,
+                             hostname,
+                             pretty_hostname,
+                             LLDP_SYSTEM_CAPABILITIES_STATION|LLDP_SYSTEM_CAPABILITIES_BRIDGE|LLDP_SYSTEM_CAPABILITIES_ROUTER,
+                             caps,
+                             &packet, &packet_size);
+        if (r < 0)
+                return r;
+
+        return lldp_send_packet(link->ifindex, packet, packet_size);
+}
+
+static int on_lldp_timer(sd_event_source *s, usec_t t, void *userdata) {
+        Link *link = userdata;
+        usec_t current, delay, next;
+        int r;
+
+        assert(s);
+        assert(userdata);
+
+        log_link_debug(link, "Sending LLDP packet...");
+
+        r = link_send_lldp(link);
+        if (r < 0)
+                log_link_debug_errno(link, r, "Failed to send LLDP packet, ignoring: %m");
+
+        if (link->lldp_tx_fast > 0)
+                link->lldp_tx_fast--;
+
+        assert_se(sd_event_now(sd_event_source_get_event(s), clock_boottime_or_monotonic(), &current) >= 0);
+
+        delay = link->lldp_tx_fast > 0 ? LLDP_FAST_TX_USEC : LLDP_TX_INTERVAL_USEC;
+        next = usec_add(usec_add(current, delay), (usec_t) random_u64() % LLDP_JITTER_USEC);
+
+        r = sd_event_source_set_time(s, next);
+        if (r < 0)
+                return log_link_error_errno(link, r, "Failed to restart LLDP timer: %m");
+
+        r = sd_event_source_set_enabled(s, SD_EVENT_ONESHOT);
+        if (r < 0)
+                return log_link_error_errno(link, r, "Failed to enable LLDP timer: %m");
+
+        return 0;
+}
+
+int link_lldp_tx_start(Link *link) {
+        usec_t next;
+        int r;
+
+        assert(link);
+
+        /* Starts the LLDP transmission in "fast" mode. If it is already started, turns "fast" mode back on again. */
+
+        link->lldp_tx_fast = LLDP_TX_FAST_INIT;
+
+        next = usec_add(usec_add(now(clock_boottime_or_monotonic()), LLDP_FAST_TX_USEC),
+                     (usec_t) random_u64() % LLDP_JITTER_USEC);
+
+        if (link->lldp_tx_event_source) {
+                usec_t old;
+
+                /* Lower the timeout, maybe */
+                r = sd_event_source_get_time(link->lldp_tx_event_source, &old);
+                if (r < 0)
+                        return r;
+
+                if (old <= next)
+                        return 0;
+
+                return sd_event_source_set_time(link->lldp_tx_event_source, next);
+        } else {
+                r = sd_event_add_time(
+                                link->manager->event,
+                                &link->lldp_tx_event_source,
+                                clock_boottime_or_monotonic(),
+                                next,
+                                0,
+                                on_lldp_timer,
+                                link);
+                if (r < 0)
+                        return r;
+
+                (void) sd_event_source_set_description(link->lldp_tx_event_source, "lldp-tx");
+        }
+
+        return 0;
+}
+
+void link_lldp_tx_stop(Link *link) {
+        assert(link);
+
+        link->lldp_tx_event_source = sd_event_source_unref(link->lldp_tx_event_source);
+}