/*
	 * Copyright (C) 2012-2025 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 <math.h>
	#include <string.h>
	#include <pthread.h>
	#include <unistd.h>
	#include <sys/uio.h>
	#include <errno.h>
	
	#include "compat.h"
	#include "compress.h"
	#include "crypto.h"
	#include "host.h"
	#include "link.h"
	#include "logging.h"
	#include "transports.h"
	#include "transport_common.h"
	#include "threads_common.h"
	#include "threads_heartbeat.h"
	#include "threads_tx.h"
	#include "netutils.h"
	
	/*
	 * SEND
	 */
	
	static int _dispatch_to_links(knet_handle_t knet_h, struct knet_host *dst_host, struct knet_mmsghdr *msg, int msgs_to_send)
	{
		int link_idx, msg_idx, sent_msgs, prev_sent, progress;
		int err = 0, savederrno = 0, locked = 0;
		unsigned int i;
		struct knet_mmsghdr *cur;
		struct knet_link *cur_link;
	
		for (link_idx = 0; link_idx < dst_host->active_link_entries; link_idx++) {
			prev_sent = 0;
			progress = 1;
			locked = 0;
	
			cur_link = &dst_host->link[dst_host->active_links[link_idx]];
	
			if (cur_link->transport == KNET_TRANSPORT_LOOPBACK) {
				continue;
			}
	
			savederrno = pthread_mutex_lock(&cur_link->link_stats_mutex);
			if (savederrno) {
				log_err(knet_h, KNET_SUB_TX, "Unable to get stats mutex lock for host %u link %u: %s",
					dst_host->host_id, cur_link->link_id, strerror(savederrno));
				continue;
			}
			locked = 1;
	
			msg_idx = 0;
			while (msg_idx < msgs_to_send) {
				msg[msg_idx].msg_hdr.msg_name = &cur_link->dst_addr;
				msg[msg_idx].msg_hdr.msg_namelen = knet_h->knet_transport_fd_tracker[cur_link->outsock].sockaddr_len;
	
				/* Cast for Linux/BSD compatibility */
				for (i=0; i<(unsigned int)msg[msg_idx].msg_hdr.msg_iovlen; i++) {
					cur_link->status.stats.tx_data_bytes += msg[msg_idx].msg_hdr.msg_iov[i].iov_len;
				}
				cur_link->status.stats.tx_data_packets++;
				msg_idx++;
			}
	
	retry:
			cur = &msg[prev_sent];
	
			sent_msgs = _sendmmsg(dst_host->link[dst_host->active_links[link_idx]].outsock,
					      transport_get_connection_oriented(knet_h, dst_host->link[dst_host->active_links[link_idx]].transport),
					      &cur[0], msgs_to_send - prev_sent, MSG_DONTWAIT | MSG_NOSIGNAL);
			savederrno = errno;
	
			err = transport_tx_sock_error(knet_h, dst_host->link[dst_host->active_links[link_idx]].transport, dst_host->link[dst_host->active_links[link_idx]].outsock, KNET_SUB_TX, sent_msgs, savederrno);
			switch(err) {
				case -1: /* unrecoverable error */
					cur_link->status.stats.tx_data_errors++;
					goto out_unlock;
					break;
				case 0: /* ignore error and continue */
					break;
				case 1: /* retry to send those same data */
					cur_link->status.stats.tx_data_retries++;
					goto retry;
					break;
			}
	
			prev_sent = prev_sent + sent_msgs;
	
			if ((sent_msgs >= 0) && (prev_sent < msgs_to_send)) {
				if ((sent_msgs) || (progress)) {
					if (sent_msgs) {
						progress = 1;
					} else {
						progress = 0;
					}
					log_trace(knet_h, KNET_SUB_TX, "Unable to send all (%d/%d) data packets to host %s (%u) link %s:%s (%u)",
						  sent_msgs, msg_idx,
						  dst_host->name, dst_host->host_id,
						  dst_host->link[dst_host->active_links[link_idx]].status.dst_ipaddr,
						  dst_host->link[dst_host->active_links[link_idx]].status.dst_port,
						  dst_host->link[dst_host->active_links[link_idx]].link_id);
					goto retry;
				}
				if (!progress) {
					savederrno = EAGAIN;
					err = -1;
					goto out_unlock;
				}
			}
	
			if ((dst_host->link_handler_policy == KNET_LINK_POLICY_RR) &&
			    (dst_host->active_link_entries > 1)) {
				uint8_t cur_link_id = dst_host->active_links[0];
	
				memmove(&dst_host->active_links[0], &dst_host->active_links[1], KNET_MAX_LINK - 1);
				dst_host->active_links[dst_host->active_link_entries - 1] = cur_link_id;
	
				break;
			}
			pthread_mutex_unlock(&cur_link->link_stats_mutex);
			locked = 0;
		}
	
	out_unlock:
		if (locked) {
			pthread_mutex_unlock(&cur_link->link_stats_mutex);
		}
		errno = savederrno;
		return err;
	}
	
	static int _parse_recv_from_sock(knet_handle_t knet_h, size_t inlen, int8_t channel, int is_sync)
	{
		size_t outlen, frag_len;
		struct knet_host *dst_host;
		knet_node_id_t dst_host_ids_temp[KNET_MAX_HOST];
		size_t dst_host_ids_entries_temp = 0;
		knet_node_id_t dst_host_ids[KNET_MAX_HOST];
		size_t dst_host_ids_entries = 0;
		int bcast = 1;
		struct iovec iov_out[PCKT_FRAG_MAX][2];
		int iovcnt_out = 2;
		uint8_t frag_idx;
		unsigned int temp_data_mtu;
		size_t host_idx;
		int send_mcast = 0;
		struct knet_header *inbuf;
		int savederrno = 0;
		int err = 0;
		seq_num_t tx_seq_num;
		struct knet_mmsghdr msg[PCKT_FRAG_MAX];
		int msgs_to_send, msg_idx;
		unsigned int i;
		int j;
		int send_local = 0;
		int data_compressed = 0;
		size_t uncrypted_frag_size;
		int stats_locked = 0, stats_err = 0;
	
		inbuf = knet_h->recv_from_sock_buf;
	
		if (knet_h->enabled != 1) {
			log_debug(knet_h, KNET_SUB_TX, "Received data packet but forwarding is disabled");
			savederrno = ECANCELED;
			err = -1;
			goto out_unlock;
		}
	
		/*
		 * move this into a separate function to expand on
		 * extra switching rules
		 */
		switch(inbuf->kh_type) {
			case KNET_HEADER_TYPE_DATA:
				if (knet_h->dst_host_filter_fn) {
					bcast = knet_h->dst_host_filter_fn(
							knet_h->dst_host_filter_fn_private_data,
							(const unsigned char *)inbuf->khp_data_userdata,
							inlen,
							KNET_NOTIFY_TX,
							knet_h->host_id,
							knet_h->host_id,
							&channel,
							dst_host_ids_temp,
							&dst_host_ids_entries_temp);
					if (bcast < 0) {
						log_debug(knet_h, KNET_SUB_TX, "Error from dst_host_filter_fn: %d", bcast);
						savederrno = EFAULT;
						err = -1;
						goto out_unlock;
					}
	
					if ((!bcast) && (!dst_host_ids_entries_temp)) {
						log_debug(knet_h, KNET_SUB_TX, "Message is unicast but no dst_host_ids_entries");
						savederrno = EINVAL;
						err = -1;
						goto out_unlock;
					}
	
					if ((!bcast) &&
					    (dst_host_ids_entries_temp > KNET_MAX_HOST)) {
						log_debug(knet_h, KNET_SUB_TX, "dst_host_filter_fn returned too many destinations");
						savederrno = EINVAL;
						err = -1;
						goto out_unlock;
					}
				}
	
				/* Send to localhost if appropriate and enabled */
				if (knet_h->has_loop_link) {
					send_local = 0;
					if (bcast) {
						send_local = 1;
					} else {
						for (i=0; i< dst_host_ids_entries_temp; i++) {
							if (dst_host_ids_temp[i] == knet_h->host_id) {
								send_local = 1;
							}
						}
					}
					if (send_local) {
						const unsigned char *buf = inbuf->khp_data_userdata;
						ssize_t buflen = inlen;
						struct knet_link *local_link;
	
						local_link = knet_h->host_index[knet_h->host_id]->link;
	
					local_retry:
						err = write(knet_h->sockfd[channel].sockfd[knet_h->sockfd[channel].is_created], buf, buflen);
						if (err < 0) {
							log_err(knet_h, KNET_SUB_TRANSP_LOOPBACK, "send local failed. error=%s\n", strerror(errno));
							local_link->status.stats.tx_data_errors++;
						}
						if (err > 0 && err < buflen) {
							log_debug(knet_h, KNET_SUB_TRANSP_LOOPBACK, "send local incomplete=%d bytes of %zu\n", err, inlen);
							local_link->status.stats.tx_data_retries++;
							buf += err;
							buflen -= err;
							goto local_retry;
						}
						if (err == buflen) {
							local_link->status.stats.tx_data_packets++;
							local_link->status.stats.tx_data_bytes += inlen;
						}
					}
				}
				break;
			default:
				log_warn(knet_h, KNET_SUB_TX, "Receiving unknown messages from socket");
				savederrno = ENOMSG;
				err = -1;
				goto out_unlock;
				break;
		}
	
		if (is_sync) {
			if ((bcast) ||
			    ((!bcast) && (dst_host_ids_entries_temp > 1))) {
				log_debug(knet_h, KNET_SUB_TX, "knet_send_sync is only supported with unicast packets for one destination");
				savederrno = E2BIG;
				err = -1;
				goto out_unlock;
			}
		}
	
		/*
		 * check destinations hosts before spending time
		 * in fragmenting/encrypting packets to save
		 * time processing data for unreachable hosts.
		 * for unicast, also remap the destination data
		 * to skip unreachable hosts.
		 */
	
		if (!bcast) {
			dst_host_ids_entries = 0;
			for (host_idx = 0; host_idx < dst_host_ids_entries_temp; host_idx++) {
				dst_host = knet_h->host_index[dst_host_ids_temp[host_idx]];
				if (!dst_host) {
					continue;
				}
				if (!(dst_host->host_id == knet_h->host_id &&
				     knet_h->has_loop_link) &&
				    dst_host->status.reachable) {
					dst_host_ids[dst_host_ids_entries] = dst_host_ids_temp[host_idx];
					dst_host_ids_entries++;
				}
			}
			if (!dst_host_ids_entries) {
				savederrno = EHOSTDOWN;
				err = -1;
				goto out_unlock;
			}
		} else {
			send_mcast = 0;
			for (dst_host = knet_h->host_head; dst_host != NULL; dst_host = dst_host->next) {
				if (!(dst_host->host_id == knet_h->host_id &&
				      knet_h->has_loop_link) &&
				    dst_host->status.reachable) {
					send_mcast = 1;
					break;
				}
			}
			if (!send_mcast) {
				savederrno = EHOSTDOWN;
				err = -1;
				goto out_unlock;
			}
		}
	
		if (!knet_h->data_mtu) {
			/*
			 * using MIN_MTU_V4 for data mtu is not completely accurate but safe enough
			 */
			log_debug(knet_h, KNET_SUB_TX,
				  "Received data packet but data MTU is still unknown."
				  " Packet might not be delivered."
				  " Assuming minimum IPv4 MTU (%d)",
				  KNET_PMTUD_MIN_MTU_V4);
			temp_data_mtu = KNET_PMTUD_MIN_MTU_V4;
		} else {
			/*
			 * take a copy of the mtu to avoid value changing under
			 * our feet while we are sending a fragmented pckt
			 */
			temp_data_mtu = knet_h->data_mtu;
		}
	
		/*
		 * compress data
		 */
		if ((knet_h->compress_model > 0) && (inlen > knet_h->compress_threshold)) {
			size_t cmp_outlen = KNET_DATABUFSIZE_COMPRESS;
			struct timespec start_time;
			struct timespec end_time;
			uint64_t compress_time;
	
			clock_gettime(CLOCK_MONOTONIC, &start_time);
			err = compress(knet_h,
				       (const unsigned char *)inbuf->khp_data_userdata, inlen,
				       knet_h->send_to_links_buf_compress, (ssize_t *)&cmp_outlen);
	
			savederrno = errno;
	
			stats_err = pthread_mutex_lock(&knet_h->handle_stats_mutex);
			if (stats_err < 0) {
				log_err(knet_h, KNET_SUB_TX, "Unable to get mutex lock: %s", strerror(stats_err));
				err = -1;
				savederrno = stats_err;
				goto out_unlock;
			}
			stats_locked = 1;
			/* Collect stats */
			clock_gettime(CLOCK_MONOTONIC, &end_time);
			timespec_diff(start_time, end_time, &compress_time);
	
			if (compress_time < knet_h->stats.tx_compress_time_min) {
				knet_h->stats.tx_compress_time_min = compress_time;
			}
			if (compress_time > knet_h->stats.tx_compress_time_max) {
				knet_h->stats.tx_compress_time_max = compress_time;
			}
			knet_h->stats.tx_compress_time_ave =
				(unsigned long long)(knet_h->stats.tx_compress_time_ave * knet_h->stats.tx_compressed_packets +
				 compress_time) / (knet_h->stats.tx_compressed_packets+1);
			if (err < 0) {
				log_warn(knet_h, KNET_SUB_COMPRESS, "Compression failed (%d): %s", err, strerror(savederrno));
			} else {
				knet_h->stats.tx_compressed_packets++;
				knet_h->stats.tx_compressed_original_bytes += inlen;
				knet_h->stats.tx_compressed_size_bytes += cmp_outlen;
	
				if (cmp_outlen < inlen) {
					memmove(inbuf->khp_data_userdata, knet_h->send_to_links_buf_compress, cmp_outlen);
					inlen = cmp_outlen;
					data_compressed = 1;
				}
			}
		}
		if (!stats_locked) {
			stats_err = pthread_mutex_lock(&knet_h->handle_stats_mutex);
			if (stats_err < 0) {
				log_err(knet_h, KNET_SUB_TX, "Unable to get mutex lock: %s", strerror(stats_err));
				err = -1;
				savederrno = stats_err;
				goto out_unlock;
			}
		}
		if (knet_h->compress_model > 0 && !data_compressed) {
			knet_h->stats.tx_uncompressed_packets++;
		}
		pthread_mutex_unlock(&knet_h->handle_stats_mutex);
		stats_locked = 0;
	
		/*
		 * prepare the outgoing buffers
		 */
	
		frag_len = inlen;
		frag_idx = 0;
	
		inbuf->khp_data_bcast = bcast;
		inbuf->khp_data_frag_num = ceil((float)inlen / temp_data_mtu);
		inbuf->khp_data_channel = channel;
		if (data_compressed) {
			inbuf->khp_data_compress = knet_h->compress_model;
		} else {
			inbuf->khp_data_compress = 0;
		}
	
		if (pthread_mutex_lock(&knet_h->tx_seq_num_mutex)) {
			log_debug(knet_h, KNET_SUB_TX, "Unable to get seq mutex lock");
			goto out_unlock;
		}
		knet_h->tx_seq_num++;
		/*
		 * force seq_num 0 to detect a node that has crashed and rejoining
		 * the knet instance. seq_num 0 will clear the buffers in the RX
		 * thread
		 */
		if (knet_h->tx_seq_num == 0) {
			knet_h->tx_seq_num++;
		}
		/*
		 * cache the value in locked context
		 */
		tx_seq_num = knet_h->tx_seq_num;
		inbuf->khp_data_seq_num = htons(knet_h->tx_seq_num);
		pthread_mutex_unlock(&knet_h->tx_seq_num_mutex);
	
		/*
		 * forcefully broadcast a ping to all nodes every SEQ_MAX / 8
		 * pckts.
		 * this solves 2 problems:
		 * 1) on TX socket overloads we generate extra pings to keep links alive
		 * 2) in 3+ nodes setup, where all the traffic is flowing between node 1 and 2,
		 *    node 3+ will be able to keep in sync on the TX seq_num even without
		 *    receiving traffic or pings in betweens. This avoids issues with
		 *    rollover of the circular buffer
		 */
	
		if (tx_seq_num % (SEQ_MAX / 8) == 0) {
			_send_pings(knet_h, 0);
		}
	
		if (inbuf->khp_data_frag_num > 1) {
			while (frag_idx < inbuf->khp_data_frag_num) {
				/*
				 * set the iov_base
				 */
				iov_out[frag_idx][0].iov_base = (void *)knet_h->send_to_links_buf[frag_idx];
				iov_out[frag_idx][0].iov_len = KNET_HEADER_DATA_SIZE;
				iov_out[frag_idx][1].iov_base = inbuf->khp_data_userdata + (temp_data_mtu * frag_idx);
	
				/*
				 * set the len
				 */
				if (frag_len > temp_data_mtu) {
					iov_out[frag_idx][1].iov_len = temp_data_mtu;
				} else {
					iov_out[frag_idx][1].iov_len = frag_len;
				}
	
				/*
				 * copy the frag info on all buffers
				 */
				knet_h->send_to_links_buf[frag_idx]->kh_type = inbuf->kh_type;
				knet_h->send_to_links_buf[frag_idx]->khp_data_seq_num = inbuf->khp_data_seq_num;
				knet_h->send_to_links_buf[frag_idx]->khp_data_frag_num = inbuf->khp_data_frag_num;
				knet_h->send_to_links_buf[frag_idx]->khp_data_bcast = inbuf->khp_data_bcast;
				knet_h->send_to_links_buf[frag_idx]->khp_data_channel = inbuf->khp_data_channel;
				knet_h->send_to_links_buf[frag_idx]->khp_data_compress = inbuf->khp_data_compress;
	
				frag_len = frag_len - temp_data_mtu;
				frag_idx++;
			}
			iovcnt_out = 2;
		} else {
			iov_out[frag_idx][0].iov_base = (void *)inbuf;
			iov_out[frag_idx][0].iov_len = frag_len + KNET_HEADER_DATA_SIZE;
			iovcnt_out = 1;
		}
	
		if (knet_h->crypto_in_use_config) {
			struct timespec start_time;
			struct timespec end_time;
			uint64_t crypt_time;
	
			frag_idx = 0;
			while (frag_idx < inbuf->khp_data_frag_num) {
				clock_gettime(CLOCK_MONOTONIC, &start_time);
				if (crypto_encrypt_and_signv(
						knet_h,
						iov_out[frag_idx], iovcnt_out,
						knet_h->send_to_links_buf_crypt[frag_idx],
						(ssize_t *)&outlen) < 0) {
					log_debug(knet_h, KNET_SUB_TX, "Unable to encrypt packet");
					savederrno = ECHILD;
					err = -1;
					goto out_unlock;
				}
				clock_gettime(CLOCK_MONOTONIC, &end_time);
				timespec_diff(start_time, end_time, &crypt_time);
	
				stats_err = pthread_mutex_lock(&knet_h->handle_stats_mutex);
				if (stats_err < 0) {
					log_err(knet_h, KNET_SUB_TX, "Unable to get mutex lock: %s", strerror(stats_err));
					err = -1;
					savederrno = stats_err;
					goto out_unlock;
				}
	
				if (crypt_time < knet_h->stats.tx_crypt_time_min) {
					knet_h->stats.tx_crypt_time_min = crypt_time;
				}
				if (crypt_time > knet_h->stats.tx_crypt_time_max) {
					knet_h->stats.tx_crypt_time_max = crypt_time;
				}
				knet_h->stats.tx_crypt_time_ave =
					(knet_h->stats.tx_crypt_time_ave * knet_h->stats.tx_crypt_packets +
					 crypt_time) / (knet_h->stats.tx_crypt_packets+1);
	
				uncrypted_frag_size = 0;
				for (j=0; j < iovcnt_out; j++) {
					uncrypted_frag_size += iov_out[frag_idx][j].iov_len;
				}
				knet_h->stats.tx_crypt_byte_overhead += (outlen - uncrypted_frag_size);
				knet_h->stats.tx_crypt_packets++;
				pthread_mutex_unlock(&knet_h->handle_stats_mutex);
	
				iov_out[frag_idx][0].iov_base = knet_h->send_to_links_buf_crypt[frag_idx];
				iov_out[frag_idx][0].iov_len = outlen;
				frag_idx++;
			}
			iovcnt_out = 1;
		}
	
		memset(&msg, 0, sizeof(msg));
	
		msgs_to_send = inbuf->khp_data_frag_num;
	
		msg_idx = 0;
	
		while (msg_idx < msgs_to_send) {
			msg[msg_idx].msg_hdr.msg_namelen = sizeof(struct sockaddr_storage); /* this will set properly in _dispatch_to_links() */
			msg[msg_idx].msg_hdr.msg_iov = &iov_out[msg_idx][0];
			msg[msg_idx].msg_hdr.msg_iovlen = iovcnt_out;
			msg_idx++;
		}
	
		if (!bcast) {
			for (host_idx = 0; host_idx < dst_host_ids_entries; host_idx++) {
				dst_host = knet_h->host_index[dst_host_ids[host_idx]];
	
				err = _dispatch_to_links(knet_h, dst_host, &msg[0], msgs_to_send);
				savederrno = errno;
				if (err) {
					goto out_unlock;
				}
			}
		} else {
			for (dst_host = knet_h->host_head; dst_host != NULL; dst_host = dst_host->next) {
				if (dst_host->status.reachable) {
					err = _dispatch_to_links(knet_h, dst_host, &msg[0], msgs_to_send);
					savederrno = errno;
					if (err) {
						goto out_unlock;
					}
				}
			}
		}
	
	out_unlock:
		errno = savederrno;
		return err;
	}
	
	static void _handle_send_to_links(knet_handle_t knet_h, struct msghdr *msg, int sockfd, int8_t channel, int type)
	{
		ssize_t inlen = 0;
		int savederrno = 0, docallback = 0;
	
		/*
		 * make sure BSD gets the right size
		 */
		msg->msg_namelen = knet_h->knet_transport_fd_tracker[sockfd].sockaddr_len;
	
		if ((channel >= 0) &&
		    (channel < KNET_DATAFD_MAX) &&
		    (!knet_h->sockfd[channel].is_socket)) {
			inlen = readv(sockfd, msg->msg_iov, 1);
		} else {
			inlen = recvmsg(sockfd, msg, MSG_DONTWAIT | MSG_NOSIGNAL);
			if (msg->msg_flags & MSG_TRUNC) {
				log_warn(knet_h, KNET_SUB_TX, "Received truncated message from sock %d. Discarding", sockfd);
				return;
			}
		}
	
		if (inlen == 0) {
			savederrno = 0;
			docallback = 1;
		} else if (inlen < 0) {
			struct epoll_event ev;
	
			savederrno = errno;
			docallback = 1;
			memset(&ev, 0, sizeof(struct epoll_event));
	
			if (epoll_ctl(knet_h->send_to_links_epollfd,
				      EPOLL_CTL_DEL, knet_h->sockfd[channel].sockfd[knet_h->sockfd[channel].is_created], &ev)) {
				log_err(knet_h, KNET_SUB_TX, "Unable to del datafd %d from linkfd epoll pool: %s",
					knet_h->sockfd[channel].sockfd[0], strerror(savederrno));
			} else {
				knet_h->sockfd[channel].has_error = 1;
			}
		} else {
			knet_h->recv_from_sock_buf->kh_type = type;
			_parse_recv_from_sock(knet_h, inlen, channel, 0);
		}
	
		if (docallback) {
			knet_h->sock_notify_fn(knet_h->sock_notify_fn_private_data,
					       knet_h->sockfd[channel].sockfd[0],
					       channel,
					       KNET_NOTIFY_TX,
					       inlen,
					       savederrno);
		}
	}
	
	void *_handle_send_to_links_thread(void *data)
	{
		knet_handle_t knet_h = (knet_handle_t) data;
		struct epoll_event events[KNET_EPOLL_MAX_EVENTS + 1]; /* see _init_epolls for + 1 */
		int i, nev, type;
		int flush, flush_queue_limit;
		int8_t channel;
		struct iovec iov_in;
		struct msghdr msg;
		struct sockaddr_storage address;
	
		set_thread_status(knet_h, KNET_THREAD_TX, KNET_THREAD_STARTED);
	
		memset(&events, 0, sizeof(events));
		memset(&iov_in, 0, sizeof(iov_in));
		iov_in.iov_base = (void *)knet_h->recv_from_sock_buf->khp_data_userdata;
		iov_in.iov_len = KNET_MAX_PACKET_SIZE;
	
		memset(&msg, 0, sizeof(struct msghdr));
		msg.msg_name = &address;
		msg.msg_namelen = sizeof(struct sockaddr_storage);
		msg.msg_iov = &iov_in;
		msg.msg_iovlen = 1;
	
		knet_h->recv_from_sock_buf->kh_version = KNET_HEADER_VERSION;
		knet_h->recv_from_sock_buf->khp_data_frag_seq = 0;
		knet_h->recv_from_sock_buf->kh_node = htons(knet_h->host_id);
	
		for (i = 0; i < (int)PCKT_FRAG_MAX; i++) {
			knet_h->send_to_links_buf[i]->kh_version = KNET_HEADER_VERSION;
			knet_h->send_to_links_buf[i]->khp_data_frag_seq = i + 1;
			knet_h->send_to_links_buf[i]->kh_node = htons(knet_h->host_id);
		}
	
		flush_queue_limit = 0;
	
		while (!shutdown_in_progress(knet_h)) {
			nev = epoll_wait(knet_h->send_to_links_epollfd, events, KNET_EPOLL_MAX_EVENTS + 1, KNET_THREADS_TIMERES / 1000);
	
			flush = get_thread_flush_queue(knet_h, KNET_THREAD_TX);
	
			/*
			 * we use timeout to detect if thread is shutting down
			 */
			if (nev == 0) {
				/*
				 * ideally we want to communicate that we are done flushing
				 * the queue when we have an epoll timeout event
				 */
				if (flush == KNET_THREAD_QUEUE_FLUSH) {
					set_thread_flush_queue(knet_h, KNET_THREAD_TX, KNET_THREAD_QUEUE_FLUSHED);
					flush_queue_limit = 0;
				}
				continue;
			}
	
			/*
			 * fall back in case the TX sockets will continue receive traffic
			 * and we do not hit an epoll timeout.
			 *
			 * allow up to a 100 loops to flush queues, then we give up.
			 * there might be more clean ways to do it by checking the buffer queue
			 * on each socket, but we have tons of sockets and calculations can go wrong.
			 * Also, why would you disable data forwarding and still send packets?
			 */
			if (flush == KNET_THREAD_QUEUE_FLUSH) {
				if (flush_queue_limit >= 100) {
					log_debug(knet_h, KNET_SUB_TX, "Timeout flushing the TX queue, expect packet loss");
					set_thread_flush_queue(knet_h, KNET_THREAD_TX, KNET_THREAD_QUEUE_FLUSHED);
					flush_queue_limit = 0;
				} else {
					flush_queue_limit++;
				}
			} else {
				flush_queue_limit = 0;
			}
	

			if (pthread_rwlock_rdlock(&knet_h->global_rwlock) != 0) {
				log_debug(knet_h, KNET_SUB_TX, "Unable to get read lock");
				continue;
			}
	
			for (i = 0; i < nev; i++) {
				type = KNET_HEADER_TYPE_DATA;
				for (channel = 0; channel < KNET_DATAFD_MAX; channel++) {
					if ((knet_h->sockfd[channel].in_use) &&
					    (knet_h->sockfd[channel].sockfd[knet_h->sockfd[channel].is_created] == events[i].data.fd)) {
						break;
					}
				}
				if (channel >= KNET_DATAFD_MAX) {
					log_debug(knet_h, KNET_SUB_TX, "No available channels");
					continue; /* channel not found */
				}

				if (pthread_mutex_lock(&knet_h->tx_mutex) != 0) {
					log_debug(knet_h, KNET_SUB_TX, "Unable to get mutex lock");
					continue;
				}
				_handle_send_to_links(knet_h, &msg, events[i].data.fd, channel, type);
				pthread_mutex_unlock(&knet_h->tx_mutex);
			}
	
			pthread_rwlock_unlock(&knet_h->global_rwlock);
		}
	
		set_thread_status(knet_h, KNET_THREAD_TX, KNET_THREAD_STOPPED);
	
		return NULL;
	}
	
	int knet_send_sync(knet_handle_t knet_h, const char *buff, const size_t buff_len, const int8_t channel)
	{
		int savederrno = 0, err = 0;
	

		if (!_is_valid_handle(knet_h)) {
			return -1;

		}
	

		if (buff == NULL) {
			errno = EINVAL;
			return -1;

		}
	

		if (buff_len <= 0) {
			errno = EINVAL;
			return -1;

		}
	

		if (buff_len > KNET_MAX_PACKET_SIZE) {
			errno = EINVAL;
			return -1;

		}
	

		if (channel < 0) {
			errno = EINVAL;
			return -1;

		}
	

		if (channel >= KNET_DATAFD_MAX) {
			errno = EINVAL;
			return -1;

		}
	

		savederrno = pthread_rwlock_rdlock(&knet_h->global_rwlock);

		if (savederrno) {
			log_err(knet_h, KNET_SUB_TX, "Unable to get read lock: %s",
				strerror(savederrno));
			errno = savederrno;
			return -1;

		}
	

		if (!knet_h->dst_host_filter_fn) {
			savederrno = ENETDOWN;
			err = -1;

			goto out;

		}
	

		if (!knet_h->sockfd[channel].in_use) {
			savederrno = EINVAL;
			err = -1;
			goto out;

		}
	

		savederrno = pthread_mutex_lock(&knet_h->tx_mutex);

		if (savederrno) {
			log_err(knet_h, KNET_SUB_TX, "Unable to get TX mutex lock: %s",
				strerror(savederrno));
			err = -1;
			goto out;

		}
	
		knet_h->recv_from_sock_buf->kh_type = KNET_HEADER_TYPE_DATA;
		memmove(knet_h->recv_from_sock_buf->khp_data_userdata, buff, buff_len);
		err = _parse_recv_from_sock(knet_h, buff_len, channel, 1);
		savederrno = errno;
	
		pthread_mutex_unlock(&knet_h->tx_mutex);
	

	out:
		pthread_rwlock_unlock(&knet_h->global_rwlock);
	

		errno = err ? savederrno : 0;
		return err;
	}
	
	ssize_t knet_send(knet_handle_t knet_h, const char *buff, const size_t buff_len, const int8_t channel)
	{
		int savederrno = 0;
		ssize_t err = 0;
		struct iovec iov_out[1];
	
		if (!_is_valid_handle(knet_h)) {
			return -1;
		}
	
		if (buff == NULL) {
			errno = EINVAL;
			return -1;
		}
	
		if (buff_len <= 0) {
			errno = EINVAL;
			return -1;
		}
	
		if (buff_len > KNET_MAX_PACKET_SIZE) {
			errno = EINVAL;
			return -1;
		}
	
		if (channel < 0) {
			errno = EINVAL;
			return -1;
		}
	
		if (channel >= KNET_DATAFD_MAX) {
			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;
		}
	
		if (!knet_h->sockfd[channel].in_use) {
			savederrno = EINVAL;
			err = -1;
			goto out_unlock;
		}
	
		memset(iov_out, 0, sizeof(iov_out));
	
		iov_out[0].iov_base = (void *)buff;
		iov_out[0].iov_len = buff_len;
	
		err = writev(knet_h->sockfd[channel].sockfd[0], iov_out, 1);
		savederrno = errno;
	
	out_unlock:
		pthread_rwlock_unlock(&knet_h->global_rwlock);
		errno = err ? savederrno : 0;
		return err;
	}