/*
	 * Copyright (C) 2015-2025 Red Hat, Inc.  All rights reserved.
	 *
	 * Authors: Fabio M. Di Nitto <fabbione@kronosnet.org>
	 *          Federico Simoncelli <fsimon@kronosnet.org>
	 *
	 * This software licensed under LGPL-2.0+
	 */
	
	#include "config.h"
	
	#include <unistd.h>
	#include <string.h>
	#include <errno.h>
	#include <pthread.h>
	
	#include "crypto.h"
	#include "links.h"
	#include "host.h"
	#include "logging.h"
	#include "transports.h"
	#include "threads_common.h"
	#include "threads_pmtud.h"
	
	static int _calculate_manual_mtu(knet_handle_t knet_h, struct knet_link *dst_link)
	{
		size_t ipproto_overhead_len;	/* onwire packet overhead (protocol based) */
	
		switch (dst_link->dst_addr.ss_family) {
			case AF_INET6:
				ipproto_overhead_len = KNET_PMTUD_OVERHEAD_V6 + dst_link->proto_overhead;
				break;
			case AF_INET:
				ipproto_overhead_len = KNET_PMTUD_OVERHEAD_V4 + dst_link->proto_overhead;
				break;
			default:
				log_debug(knet_h, KNET_SUB_PMTUD, "unknown protocol");
				return 0;
				break;
		}
	
		dst_link->status.mtu = calc_max_data_outlen(knet_h, knet_h->manual_mtu - ipproto_overhead_len);
	
		return 1;
	}
	
	static int _handle_check_link_pmtud(knet_handle_t knet_h, struct knet_host *dst_host, struct knet_link *dst_link)
	{
		int err, ret, savederrno, mutex_retry_limit, failsafe, use_kernel_mtu, warn_once;
		uint32_t kernel_mtu;		/* record kernel_mtu from EMSGSIZE */
		size_t onwire_len;   		/* current packet onwire size */
		size_t ipproto_overhead_len;	/* onwire packet overhead (protocol based) */
		size_t max_mtu_len;		/* max mtu for protocol */
		size_t data_len;		/* how much data we can send in the packet
						 * generally would be onwire_len - ipproto_overhead_len
						 * needs to be adjusted for crypto
						 */
		size_t app_mtu_len;		/* real data that we can send onwire */
		ssize_t len;			/* len of what we were able to sendto onwire */
	
		struct timespec ts, pmtud_crypto_start_ts, pmtud_crypto_stop_ts;
		unsigned long long pong_timeout_adj_tmp, timediff;
		int pmtud_crypto_reduce = 1;
		unsigned char *outbuf = (unsigned char *)knet_h->pmtudbuf;
	
		warn_once = 0;
	
		mutex_retry_limit = 0;
		failsafe = 0;
	
		knet_h->pmtudbuf->khp_pmtud_link = dst_link->link_id;
	
		switch (dst_link->dst_addr.ss_family) {
			case AF_INET6:
				max_mtu_len = KNET_PMTUD_SIZE_V6;
				ipproto_overhead_len = KNET_PMTUD_OVERHEAD_V6 + dst_link->proto_overhead;
				break;
			case AF_INET:
				max_mtu_len = KNET_PMTUD_SIZE_V4;
				ipproto_overhead_len = KNET_PMTUD_OVERHEAD_V4 + dst_link->proto_overhead;
				break;
			default:
				log_debug(knet_h, KNET_SUB_PMTUD, "PMTUD aborted, unknown protocol");
				return -1;
				break;
		}
	
		dst_link->last_bad_mtu = 0;
		dst_link->last_good_mtu = dst_link->last_ping_size + ipproto_overhead_len;
	
		/*
		 * discovery starts from the top because kernel will
		 * refuse to send packets > current iface mtu.
		 * this saves us some time and network bw.
		 */ 
		onwire_len = max_mtu_len;
	
	restart:
	
		/*
		 * prevent a race when interface mtu is changed _exactly_ during
		 * the discovery process and it's complex to detect. Easier
		 * to wait the next loop.
		 * 30 is not an arbitrary value. To bisect from 576 to 128000 doesn't
		 * take more than 18/19 steps.
		 */
	
		if (failsafe == 30) {
			log_err(knet_h, KNET_SUB_PMTUD,
				"Aborting PMTUD process: Too many attempts. MTU might have changed during discovery.");
			return -1;
		} else {
			failsafe++;
		}
	
		/*
		 * common to all packets
		 */
	
		/*
		 * calculate the application MTU based on current onwire_len minus ipproto_overhead_len
		 */
	
		app_mtu_len = calc_max_data_outlen(knet_h, onwire_len - ipproto_overhead_len);
	
		/*
		 * recalculate onwire len back that might be different based
		 * on data padding from crypto layer.
		 */
	
		onwire_len = calc_data_outlen(knet_h, app_mtu_len + KNET_HEADER_ALL_SIZE) + ipproto_overhead_len;
	
		/*
		 * calculate the size of what we need to send to sendto(2).
		 * see also onwire.c for packet format explanation.
		 */
		data_len = app_mtu_len + knet_h->sec_hash_size + knet_h->sec_salt_size + KNET_HEADER_ALL_SIZE;
	
		if (knet_h->crypto_in_use_config) {
			if (data_len < (knet_h->sec_hash_size + knet_h->sec_salt_size) + 1) {
				log_debug(knet_h, KNET_SUB_PMTUD, "Aborting PMTUD process: link mtu smaller than crypto header detected (link might have been disconnected)");
				return -1;
			}
	
			knet_h->pmtudbuf->khp_pmtud_size = onwire_len;
	
			if (crypto_encrypt_and_sign(knet_h,
						    (const unsigned char *)knet_h->pmtudbuf,
						    data_len - (knet_h->sec_hash_size + knet_h->sec_salt_size),
						    knet_h->pmtudbuf_crypt,
						    (ssize_t *)&data_len) < 0) {
				log_debug(knet_h, KNET_SUB_PMTUD, "Unable to crypto pmtud packet");
				return -1;
			}
	
			outbuf = knet_h->pmtudbuf_crypt;
			if (pthread_mutex_lock(&knet_h->handle_stats_mutex) < 0) {
				log_err(knet_h, KNET_SUB_PMTUD, "Unable to get mutex lock");
				return -1;
			}
			knet_h->stats_extra.tx_crypt_pmtu_packets++;
			pthread_mutex_unlock(&knet_h->handle_stats_mutex);
		} else {
			knet_h->pmtudbuf->khp_pmtud_size = onwire_len;
		}
	
		/* link has gone down, aborting pmtud */
		if (dst_link->status.connected != 1) {
			log_debug(knet_h, KNET_SUB_PMTUD, "PMTUD detected host (%u) link (%u) has been disconnected", dst_host->host_id, dst_link->link_id);
			return -1;
		}
	
		if (dst_link->transport_connected != 1) {
			log_debug(knet_h, KNET_SUB_PMTUD, "PMTUD detected host (%u) link (%u) has been disconnected", dst_host->host_id, dst_link->link_id);
			return -1;
		}
	
		if (pthread_mutex_lock(&knet_h->pmtud_mutex) != 0) {
			log_debug(knet_h, KNET_SUB_PMTUD, "Unable to get mutex lock");
			return -1;
		}
	
		if (knet_h->pmtud_abort) {
			pthread_mutex_unlock(&knet_h->pmtud_mutex);
			errno = EDEADLK;
			return -1;
		}
	
		savederrno = pthread_mutex_lock(&knet_h->tx_mutex);
		if (savederrno) {
			pthread_mutex_unlock(&knet_h->pmtud_mutex);
			log_err(knet_h, KNET_SUB_PMTUD, "Unable to get TX mutex lock: %s", strerror(savederrno));
			return -1;
		}
	
		savederrno = pthread_mutex_lock(&dst_link->link_stats_mutex);
		if (savederrno) {
			pthread_mutex_unlock(&knet_h->pmtud_mutex);
			pthread_mutex_unlock(&knet_h->tx_mutex);
			log_err(knet_h, KNET_SUB_PMTUD, "Unable to get stats mutex lock for host %u link %u: %s",
				dst_host->host_id, dst_link->link_id, strerror(savederrno));
			return -1;
		}
	
	retry:
		if (transport_get_connection_oriented(knet_h, dst_link->transport) == TRANSPORT_PROTO_NOT_CONNECTION_ORIENTED) {
			len = sendto(dst_link->outsock, outbuf, data_len, MSG_DONTWAIT | MSG_NOSIGNAL,
				     (struct sockaddr *) &dst_link->dst_addr,
				     knet_h->knet_transport_fd_tracker[dst_link->outsock].sockaddr_len);
		} else {
			len = sendto(dst_link->outsock, outbuf, data_len, MSG_DONTWAIT | MSG_NOSIGNAL, NULL, 0);
		}
		savederrno = errno;
	
		/*
		 * we cannot hold a lock on kmtu_mutex between resetting
		 * knet_h->kernel_mtu here and below where it's used.
		 * use_kernel_mtu tells us if the knet_h->kernel_mtu was
		 * set to 0 and we can trust its value later.
		 */
		use_kernel_mtu = 0;
	
		if (pthread_mutex_lock(&knet_h->kmtu_mutex) == 0) {
			use_kernel_mtu = 1;
			knet_h->kernel_mtu = 0;
			pthread_mutex_unlock(&knet_h->kmtu_mutex);
		}
	
		kernel_mtu = 0;
	
		err = transport_tx_sock_error(knet_h, dst_link->transport, dst_link->outsock, KNET_SUB_PMTUD, len, savederrno);
		switch(err) {
			case -1: /* unrecoverable error */
				log_debug(knet_h, KNET_SUB_PMTUD, "Unable to send pmtu packet (sendto): %d %s", savederrno, strerror(savederrno));
				pthread_mutex_unlock(&knet_h->tx_mutex);
				pthread_mutex_unlock(&knet_h->pmtud_mutex);
				dst_link->status.stats.tx_pmtu_errors++;
				pthread_mutex_unlock(&dst_link->link_stats_mutex);
				return -1;
			case 0: /* ignore error and continue */
				break;
			case 1: /* retry to send those same data */
				dst_link->status.stats.tx_pmtu_retries++;
				goto retry;
				break;
		}
	
		pthread_mutex_unlock(&knet_h->tx_mutex);
	
		if (len != (ssize_t )data_len) {
			pthread_mutex_unlock(&dst_link->link_stats_mutex);
			if (savederrno == EMSGSIZE || savederrno == EPERM) {
				/*
				 * we cannot hold a lock on kmtu_mutex between resetting
				 * knet_h->kernel_mtu and here.
				 * use_kernel_mtu tells us if the knet_h->kernel_mtu was
				 * set to 0 previously and we can trust its value now.
				 */
				if (use_kernel_mtu) {
					use_kernel_mtu = 0;
					if (pthread_mutex_lock(&knet_h->kmtu_mutex) == 0) {
						kernel_mtu = knet_h->kernel_mtu;
						pthread_mutex_unlock(&knet_h->kmtu_mutex);
					}
				}
				if (kernel_mtu > 0) {
					dst_link->last_bad_mtu = kernel_mtu + 1;
				} else {
					dst_link->last_bad_mtu = onwire_len;
				}
			} else {
				log_debug(knet_h, KNET_SUB_PMTUD, "Unable to send pmtu packet len: %zu err: %s", onwire_len, strerror(savederrno));
			}
	
		} else {
			dst_link->last_sent_mtu = onwire_len;
			dst_link->last_recv_mtu = 0;
			dst_link->status.stats.tx_pmtu_packets++;
			dst_link->status.stats.tx_pmtu_bytes += data_len;
			pthread_mutex_unlock(&dst_link->link_stats_mutex);
	
			if (clock_gettime(CLOCK_REALTIME, &ts) < 0) {
				log_debug(knet_h, KNET_SUB_PMTUD, "Unable to get current time: %s", strerror(errno));
				pthread_mutex_unlock(&knet_h->pmtud_mutex);
				return -1;
			}
	
			/*
			 * non fatal, we can wait the next round to reduce the
			 * multiplier
			 */
			if (clock_gettime(CLOCK_MONOTONIC, &pmtud_crypto_start_ts) < 0) {
				log_debug(knet_h, KNET_SUB_PMTUD, "Unable to get current time: %s", strerror(errno));
				pmtud_crypto_reduce = 0;
			}
	
			/*
			 * set PMTUd reply timeout to match pong_timeout on a given link
			 *
			 * math: internally pong_timeout is expressed in microseconds, while
			 *       the public API exports milliseconds. So careful with the 0's here.
			 * the loop is necessary because we are grabbing the current time just above
			 * and add values to it that could overflow into seconds.
			 */ 
	
			if (pthread_mutex_lock(&knet_h->backoff_mutex)) {
				log_debug(knet_h, KNET_SUB_PMTUD, "Unable to get backoff_mutex");
				pthread_mutex_unlock(&knet_h->pmtud_mutex);
				return -1;
			}
	
			if (knet_h->crypto_in_use_config) {
				/*
				 * crypto, under pressure, is a royal PITA
				 */
				pong_timeout_adj_tmp = dst_link->pong_timeout_adj * dst_link->pmtud_crypto_timeout_multiplier;
			} else {
				pong_timeout_adj_tmp = dst_link->pong_timeout_adj;
			}
	
			ts.tv_sec += pong_timeout_adj_tmp / 1000000;
			ts.tv_nsec += (((pong_timeout_adj_tmp) % 1000000) * 1000);
			while (ts.tv_nsec > 1000000000) {
				ts.tv_sec += 1;
				ts.tv_nsec -= 1000000000;
			}
	
			pthread_mutex_unlock(&knet_h->backoff_mutex);
	
			knet_h->pmtud_waiting = 1;
	
			ret = pthread_cond_timedwait(&knet_h->pmtud_cond, &knet_h->pmtud_mutex, &ts);
	
			knet_h->pmtud_waiting = 0;
	
			if (knet_h->pmtud_abort) {
				pthread_mutex_unlock(&knet_h->pmtud_mutex);
				errno = EDEADLK;
				return -1;
			}
	
			/*
			 * we cannot use shutdown_in_progress in here because
			 * we already hold the read lock
			 */
			if (knet_h->fini_in_progress) {
				pthread_mutex_unlock(&knet_h->pmtud_mutex);
				log_debug(knet_h, KNET_SUB_PMTUD, "PMTUD aborted. shutdown in progress");
				return -1;
			}
	
			if (ret) {
				if (ret == ETIMEDOUT) {
					if ((knet_h->crypto_in_use_config) && (dst_link->pmtud_crypto_timeout_multiplier < KNET_LINK_PMTUD_CRYPTO_TIMEOUT_MULTIPLIER_MAX)) {
						dst_link->pmtud_crypto_timeout_multiplier = dst_link->pmtud_crypto_timeout_multiplier * 2;
						pmtud_crypto_reduce = 0;
						log_debug(knet_h, KNET_SUB_PMTUD,
								"Increasing PMTUd response timeout multiplier to (%u) for host %u link: %u",
								dst_link->pmtud_crypto_timeout_multiplier,
								dst_host->host_id,
								dst_link->link_id);
						pthread_mutex_unlock(&knet_h->pmtud_mutex);
						goto restart;
					}
					if (!warn_once) {
						log_warn(knet_h, KNET_SUB_PMTUD,
								"possible MTU misconfiguration detected. "
								"kernel is reporting MTU: %u bytes for "
								"host %u link %u but the other node is "
								"not acknowledging packets of this size. ",
								dst_link->last_sent_mtu,
								dst_host->host_id,
								dst_link->link_id);
						log_warn(knet_h, KNET_SUB_PMTUD,
								"This can be caused by this node interface MTU "
								"too big or a network device that does not "
								"support or has been misconfigured to manage MTU "
								"of this size, or packet loss. knet will continue "
								"to run but performances might be affected.");
						warn_once = 1;
					}
				} else {
					pthread_mutex_unlock(&knet_h->pmtud_mutex);
					if (mutex_retry_limit == 3) {
						log_debug(knet_h, KNET_SUB_PMTUD, "PMTUD aborted, unable to get mutex lock");
						return -1;
					}
					mutex_retry_limit++;
					goto restart;
				}
			}
	
			if ((knet_h->crypto_in_use_config) && (pmtud_crypto_reduce == 1) &&
			    (dst_link->pmtud_crypto_timeout_multiplier > KNET_LINK_PMTUD_CRYPTO_TIMEOUT_MULTIPLIER_MIN)) {
				if (!clock_gettime(CLOCK_MONOTONIC, &pmtud_crypto_stop_ts)) {
					timespec_diff(pmtud_crypto_start_ts, pmtud_crypto_stop_ts, &timediff);
					if (((pong_timeout_adj_tmp * 1000) / 2) > timediff) {
						dst_link->pmtud_crypto_timeout_multiplier = dst_link->pmtud_crypto_timeout_multiplier / 2;
						log_debug(knet_h, KNET_SUB_PMTUD,
								"Decreasing PMTUd response timeout multiplier to (%u) for host %u link: %u",
								dst_link->pmtud_crypto_timeout_multiplier,
								dst_host->host_id,
								dst_link->link_id);
					}
				} else {
					log_debug(knet_h, KNET_SUB_PMTUD, "Unable to get current time: %s", strerror(errno));
				}
			}
	
			if ((dst_link->last_recv_mtu != onwire_len) || (ret)) {
				dst_link->last_bad_mtu = onwire_len;
			} else {
				int found_mtu = 0;
	
				if (knet_h->sec_block_size) {
					if ((onwire_len + knet_h->sec_block_size >= max_mtu_len) ||
					   ((dst_link->last_bad_mtu) && (dst_link->last_bad_mtu <= (onwire_len + knet_h->sec_block_size)))) {
						found_mtu = 1;
					}
				} else {
					if ((onwire_len == max_mtu_len) ||
					    ((dst_link->last_bad_mtu) && (dst_link->last_bad_mtu == (onwire_len + 1))) ||
					     (dst_link->last_bad_mtu == dst_link->last_good_mtu)) {
						found_mtu = 1;
					}
				}
	
				if (found_mtu) {
					/*
					 * account for IP overhead, knet headers and crypto in PMTU calculation
					 */
					dst_link->status.mtu = calc_max_data_outlen(knet_h, onwire_len - ipproto_overhead_len);
					pthread_mutex_unlock(&knet_h->pmtud_mutex);
					return 0;
				}
	
				dst_link->last_good_mtu = onwire_len;
			}
		}
	
		if (kernel_mtu) {
			onwire_len = kernel_mtu;
		} else {
			onwire_len = (dst_link->last_good_mtu + dst_link->last_bad_mtu) / 2;
		}
	
		pthread_mutex_unlock(&knet_h->pmtud_mutex);
	
		goto restart;
	}
	
	static int _handle_check_pmtud(knet_handle_t knet_h, struct knet_host *dst_host, struct knet_link *dst_link, int force_run)
	{
		uint8_t saved_valid_pmtud;
		unsigned int saved_pmtud;
		struct timespec clock_now;
		unsigned long long diff_pmtud, interval;
	
		if (clock_gettime(CLOCK_MONOTONIC, &clock_now) != 0) {
			log_debug(knet_h, KNET_SUB_PMTUD, "Unable to get monotonic clock");
			return 0;
		}
	
		if (!force_run) {
			interval = knet_h->pmtud_interval * 1000000000llu; /* nanoseconds */
	
			timespec_diff(dst_link->pmtud_last, clock_now, &diff_pmtud);
	
			if (diff_pmtud < interval) {
				return dst_link->has_valid_mtu;
			}
		}
	
		/*
		 * status.proto_overhead should include all IP/(UDP|SCTP)/knet headers
		 *
		 * please note that it is not the same as link->proto_overhead that
		 * includes only either UDP or SCTP (at the moment) overhead.
		 */
		switch (dst_link->dst_addr.ss_family) {
			case AF_INET6:
				dst_link->status.proto_overhead = KNET_PMTUD_OVERHEAD_V6 + dst_link->proto_overhead + KNET_HEADER_ALL_SIZE + knet_h->sec_hash_size + knet_h->sec_salt_size;
				break;
			case AF_INET:
				dst_link->status.proto_overhead = KNET_PMTUD_OVERHEAD_V4 + dst_link->proto_overhead + KNET_HEADER_ALL_SIZE + knet_h->sec_hash_size + knet_h->sec_salt_size;
				break;
		}
	
		saved_pmtud = dst_link->status.mtu;
		saved_valid_pmtud = dst_link->has_valid_mtu;
	
		log_debug(knet_h, KNET_SUB_PMTUD, "Starting PMTUD for host: %u link: %u", dst_host->host_id, dst_link->link_id);
	
		errno = 0;
		if (_handle_check_link_pmtud(knet_h, dst_host, dst_link) < 0) {
			if (errno == EDEADLK) {
				log_debug(knet_h, KNET_SUB_PMTUD, "PMTUD for host: %u link: %u has been rescheduled", dst_host->host_id, dst_link->link_id);
				dst_link->status.mtu = saved_pmtud;
				dst_link->has_valid_mtu = saved_valid_pmtud;
				errno = EDEADLK;
				return dst_link->has_valid_mtu;
			}
			dst_link->has_valid_mtu = 0;
		} else {
			if (dst_link->status.mtu < calc_min_mtu(knet_h)) {
				log_info(knet_h, KNET_SUB_PMTUD,
					 "Invalid MTU detected for host: %u link: %u mtu: %u",
					 dst_host->host_id, dst_link->link_id, dst_link->status.mtu);
				dst_link->has_valid_mtu = 0;
			} else {
				dst_link->has_valid_mtu = 1;
			}
			if (dst_link->has_valid_mtu) {
				if ((saved_pmtud) && (saved_pmtud != dst_link->status.mtu)) {
					log_info(knet_h, KNET_SUB_PMTUD, "PMTUD link change for host: %u link: %u from %u to %u",
						 dst_host->host_id, dst_link->link_id, saved_pmtud, dst_link->status.mtu);
				}
				log_debug(knet_h, KNET_SUB_PMTUD, "PMTUD completed for host: %u link: %u current link mtu: %u",
					  dst_host->host_id, dst_link->link_id, dst_link->status.mtu);
	
				/*
				 * set pmtud_last, if we can, after we are done with the PMTUd process
				 * because it can take a very long time.
				 */
				dst_link->pmtud_last = clock_now;
				if (!clock_gettime(CLOCK_MONOTONIC, &clock_now)) {
					dst_link->pmtud_last = clock_now;
				}
			}
		}
	
		if (saved_valid_pmtud != dst_link->has_valid_mtu) {
			_host_dstcache_update_async(knet_h, dst_host);
		}
	
		return dst_link->has_valid_mtu;
	}
	
	void *_handle_pmtud_link_thread(void *data)
	{
		knet_handle_t knet_h = (knet_handle_t) data;
		struct knet_host *dst_host;
		struct knet_link *dst_link;
		int link_idx;
		unsigned int have_mtu;
		unsigned int lower_mtu;
		int link_has_mtu;
		int force_run = 0;
	
		set_thread_status(knet_h, KNET_THREAD_PMTUD, KNET_THREAD_STARTED);
	
		knet_h->data_mtu = calc_min_mtu(knet_h);
	
		/* preparing pmtu buffer */
		knet_h->pmtudbuf->kh_version = KNET_HEADER_VERSION;
		knet_h->pmtudbuf->kh_type = KNET_HEADER_TYPE_PMTUD;
		knet_h->pmtudbuf->kh_node = htons(knet_h->host_id);
	
		while (!shutdown_in_progress(knet_h)) {
			usleep(KNET_THREADS_TIMERES);
	

			if (pthread_mutex_lock(&knet_h->pmtud_mutex) != 0) {
				log_debug(knet_h, KNET_SUB_PMTUD, "Unable to get mutex lock");
				continue;
			}
			knet_h->pmtud_abort = 0;

			knet_h->pmtud_running = 1;
			force_run = knet_h->pmtud_forcerun;
			knet_h->pmtud_forcerun = 0;
			pthread_mutex_unlock(&knet_h->pmtud_mutex);
	
			if (force_run) {
				log_debug(knet_h, KNET_SUB_PMTUD, "PMTUd request to rerun has been received");
			}
	
			if (pthread_rwlock_rdlock(&knet_h->global_rwlock) != 0) {
				log_debug(knet_h, KNET_SUB_PMTUD, "Unable to get read lock");
				continue;
			}
	
			lower_mtu = KNET_PMTUD_SIZE_V4;
			have_mtu = 0;
	
			for (dst_host = knet_h->host_head; dst_host != NULL; dst_host = dst_host->next) {
				for (link_idx = 0; link_idx < KNET_MAX_LINK; link_idx++) {
					dst_link = &dst_host->link[link_idx];
	
					if ((dst_link->status.enabled != 1) ||
					    (dst_link->status.connected != 1) ||
					    (dst_host->link[link_idx].transport == KNET_TRANSPORT_LOOPBACK) ||
					    (!dst_link->last_ping_size) ||
					    ((dst_link->dynamic == KNET_LINK_DYNIP) &&
					     (dst_link->status.dynconnected != 1)))
						continue;
	
					if (!knet_h->manual_mtu) {
						link_has_mtu = _handle_check_pmtud(knet_h, dst_host, dst_link, force_run);
						if (errno == EDEADLK) {
							goto out_unlock;
						}
						if (link_has_mtu) {
							have_mtu = 1;
							if (dst_link->status.mtu < lower_mtu) {
								lower_mtu = dst_link->status.mtu;
							}
						}
					} else {
						link_has_mtu = _calculate_manual_mtu(knet_h, dst_link);
						if (link_has_mtu) {
							have_mtu = 1;
							if (dst_link->status.mtu < lower_mtu) {
								lower_mtu = dst_link->status.mtu;
							}
						}
					}
				}
			}
	
			if (have_mtu) {
				if (knet_h->data_mtu != lower_mtu) {
					knet_h->data_mtu = lower_mtu;
					log_info(knet_h, KNET_SUB_PMTUD, "Global data MTU changed to: %u", knet_h->data_mtu);
	
					if (knet_h->pmtud_notify_fn) {
						knet_h->pmtud_notify_fn(knet_h->pmtud_notify_fn_private_data,
									knet_h->data_mtu);
					}
				}
			}
	out_unlock:
			pthread_rwlock_unlock(&knet_h->global_rwlock);

			if (pthread_mutex_lock(&knet_h->pmtud_mutex) != 0) {
				log_debug(knet_h, KNET_SUB_PMTUD, "Unable to get mutex lock");
			} else {

				knet_h->pmtud_running = 0;
				pthread_mutex_unlock(&knet_h->pmtud_mutex);
			}
		}
	
		set_thread_status(knet_h, KNET_THREAD_PMTUD, KNET_THREAD_STOPPED);
	
		return NULL;
	}
	
	int knet_handle_pmtud_getfreq(knet_handle_t knet_h, unsigned int *interval)
	{
		int savederrno = 0;
	
		if (!_is_valid_handle(knet_h)) {
			return -1;
		}
	
		if (!interval) {
			errno = EINVAL;
			return -1;
		}
	
		savederrno = pthread_rwlock_rdlock(&knet_h->global_rwlock);
		if (savederrno) {
			log_err(knet_h, KNET_SUB_HANDLE, "Unable to get read lock: %s",
				strerror(savederrno));
			errno = savederrno;
			return -1;
		}
	
		*interval = knet_h->pmtud_interval;
	
		pthread_rwlock_unlock(&knet_h->global_rwlock);
	
		errno = 0;
		return 0;
	}
	
	int knet_handle_pmtud_setfreq(knet_handle_t knet_h, unsigned int interval)
	{
		int savederrno = 0;
	
		if (!_is_valid_handle(knet_h)) {
			return -1;
		}
	
		if ((!interval) || (interval > 86400)) {
			errno = EINVAL;
			return -1;
		}
	
		savederrno = get_global_wrlock(knet_h);
		if (savederrno) {
			log_err(knet_h, KNET_SUB_HANDLE, "Unable to get write lock: %s",
				strerror(savederrno));
			errno = savederrno;
			return -1;
		}
	
		knet_h->pmtud_interval = interval;
		log_debug(knet_h, KNET_SUB_HANDLE, "PMTUd interval set to: %u seconds", interval);
	
		pthread_rwlock_unlock(&knet_h->global_rwlock);
	
		errno = 0;
		return 0;
	}
	
	int knet_handle_enable_pmtud_notify(knet_handle_t knet_h,
					    void *pmtud_notify_fn_private_data,
					    void (*pmtud_notify_fn) (
							void *private_data,
							unsigned int data_mtu))
	{
		int savederrno = 0;
	
		if (!_is_valid_handle(knet_h)) {
			return -1;
		}
	
		savederrno = get_global_wrlock(knet_h);
		if (savederrno) {
			log_err(knet_h, KNET_SUB_HANDLE, "Unable to get write lock: %s",
				strerror(savederrno));
			errno = savederrno;
			return -1;
		}
	
		knet_h->pmtud_notify_fn_private_data = pmtud_notify_fn_private_data;
		knet_h->pmtud_notify_fn = pmtud_notify_fn;
		if (knet_h->pmtud_notify_fn) {
			log_debug(knet_h, KNET_SUB_HANDLE, "pmtud_notify_fn enabled");
		} else {
			log_debug(knet_h, KNET_SUB_HANDLE, "pmtud_notify_fn disabled");
		}
	
		pthread_rwlock_unlock(&knet_h->global_rwlock);
	
		errno = 0;
		return 0;
	}
	
	int knet_handle_pmtud_set(knet_handle_t knet_h,
				  unsigned int iface_mtu)
	{
		int savederrno = 0;
	
		if (!_is_valid_handle(knet_h)) {
			return -1;
		}
	
		if (iface_mtu > KNET_PMTUD_SIZE_V4) {
			errno = EINVAL;
			return -1;
		}
	
		savederrno = pthread_rwlock_rdlock(&knet_h->global_rwlock);
		if (savederrno) {
			log_err(knet_h, KNET_SUB_PMTUD, "Unable to get read lock: %s",
				strerror(savederrno));
			errno = savederrno;
			return -1;
		}
	
		log_info(knet_h, KNET_SUB_PMTUD, "MTU manually set to: %u", iface_mtu);
	
		knet_h->manual_mtu = iface_mtu;
	
		force_pmtud_run(knet_h, KNET_SUB_PMTUD, 0, 0);
	
		pthread_rwlock_unlock(&knet_h->global_rwlock);
	
		errno = 0;
		return 0;
	}
	
	int knet_handle_pmtud_get(knet_handle_t knet_h,
				  unsigned int *data_mtu)
	{
		int savederrno = 0;
	
		if (!_is_valid_handle(knet_h)) {
			return -1;
		}
	
		if (!data_mtu) {
			errno = EINVAL;
			return -1;
		}
	
		savederrno = pthread_rwlock_rdlock(&knet_h->global_rwlock);
		if (savederrno) {
			log_err(knet_h, KNET_SUB_HANDLE, "Unable to get read lock: %s",
				strerror(savederrno));
			errno = savederrno;
			return -1;
		}
	
		*data_mtu = knet_h->data_mtu;
	
		pthread_rwlock_unlock(&knet_h->global_rwlock);
	
		errno = 0;
		return 0;
	}