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/* SPDX-License-Identifier: GPL-3.0-or-later */
#include "mpu.h"
#include "heap.h"
#include <errno.h>
#include <stddef.h>
#include <stdint.h>
#include <string.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <sys/poll.h>
#include <time.h>
int mpu_init(mpu_ctx_t* ctx,
int sock0, float weight0,
int sock1, float weight1,
int reorder_window,
size_t reorder_slots
) {
if (!ctx || sock0 < 0 || sock1 < 0
|| weight0 <= 0.0F || weight1 <= 0.0F
|| reorder_window <= 0
|| reorder_slots == 0) {
errno = EINVAL;
return -1;
}
ctx->paths[0] = (mpu_path_t) {
.sockfd = sock0,
.weight = weight0
};
ctx->paths[1] = (mpu_path_t) {
.sockfd = sock1,
.weight = weight1
};
ctx->credits[0] = 0.0F;
ctx->credits[1] = 0.0F;
ctx->send_seq_num = 1;
ctx->recv_seq_num = 1;
ctx->reorder_window = reorder_window;
int i = heap_init(&ctx->reorder_heap, reorder_slots, sizeof(mpu_slot_t));
if (i < 0) {
return -1;
}
return 0;
}
// Helper to get current time in milliseconds
static inline uint64_t get_time_now(void) {
struct timespec ts;
clock_gettime(CLOCK_MONOTONIC, &ts);
return (uint64_t) ts.tv_sec * 1000ULL
+ ((uint64_t) ts.tv_nsec / 1000000ULL);
}
// FIXME: seq_num is never converted to network byte order
// TODO: Zero-copy send() requiring the user to reserve space for the header.
// Perhaps consider MSG_MORE for sending header & payload separately or sendmsg()
int mpu_send(mpu_ctx_t* ctx, const uint8_t* data, size_t len) {
if (!ctx || !data || len == 0 || len > MPU_MTU - sizeof(mpu_hdr_t)) {
errno = EINVAL;
return -1;
}
// Prepare packet with header
size_t packet_len = sizeof(mpu_hdr_t) + len;
union {
uint8_t buf[MPU_MTU];
mpu_hdr_t hdr;
} packet;
memcpy(packet.buf + sizeof(mpu_hdr_t), data, len);
packet.hdr = (mpu_hdr_t) {
.seq_num = ctx->send_seq_num++
};
// Select path using weighted round-robin scheduler
int path_idx = (ctx->credits[0] <= ctx->credits[1]) ? 0 : 1;
ctx->credits[path_idx] += (float) len / ctx->paths[path_idx].weight;
ssize_t sent = send(ctx->paths[path_idx].sockfd, packet.buf, packet_len, 0);
if (sent < 0) {
return -1;
}
return 0;
}
// FIXME: Skipped packages are never purged
// TODO: Zero-copy recv() into reorder buffer slot, requiring the user to provide a callback
// for processing received packets, instead of copying into a user buffer.
// TODO: Attempt to optimize heap_extract() to purge multiple expired packets at once.
ssize_t mpu_recv(mpu_ctx_t* ctx, uint8_t* data, size_t len) {
if (!ctx || !data || !len) {
errno = EINVAL;
return -1;
}
while (true) {
// Peek heap for next in-order packet and deliver if available
heap_node_t* node = heap_next_extract(&ctx->reorder_heap);
if (node && node->value == ctx->recv_seq_num) {
mpu_slot_t* slot = (mpu_slot_t*) node->user;
size_t data_len = slot->packet_len - sizeof(mpu_hdr_t);
if (data_len > len) {
data_len = len;
}
memcpy(data, slot->packet.buf + sizeof(mpu_hdr_t), data_len);
heap_extract(&ctx->reorder_heap);
ctx->recv_seq_num++;
return (ssize_t) data_len;
}
// Purge packets outside of reorder window from heap
uint64_t now = get_time_now();
int expires_in = ctx->reorder_window;
while (true) {
node = heap_next_extract(&ctx->reorder_heap);
if (!node) {
break;
}
mpu_slot_t* slot = (mpu_slot_t*) node->user;
int age = (int) (now - slot->timestamp);
if (age < ctx->reorder_window) {
expires_in = ctx->reorder_window - age;
break;
}
ctx->recv_seq_num = slot->packet.hdr.seq_num + 1;
heap_extract(&ctx->reorder_heap);
}
// Receive from either path
struct pollfd pfds[2] = {
{ .fd = ctx->paths[0].sockfd, .events = POLLIN },
{ .fd = ctx->paths[1].sockfd, .events = POLLIN }
};
int ret = poll(pfds, 2, expires_in);
if (ret < 0) {
if (errno == EINTR) {
continue;
}
return -1;
} else if (ret == 0) {
continue;
}
for (int i = 0; i < 2; i++) {
if (!(pfds[i].revents & POLLIN)) {
continue;
}
// Write to reorder buffer
node = heap_next_insert(&ctx->reorder_heap);
if (!node) {
// No free slot, skip packet for now
continue;
}
mpu_slot_t* slot = (mpu_slot_t*) node->user;
ssize_t packet_len = recv(pfds[i].fd, slot->packet.buf, MPU_MTU, 0);
if (packet_len < 0) {
if (errno == EINTR) {
continue;
}
return -1;
} else if (packet_len < (ssize_t) sizeof(mpu_hdr_t)) {
// Malformed packet, ignore
continue;
}
slot->timestamp = get_time_now();
slot->packet_len = (uint16_t) packet_len;
heap_insert(&ctx->reorder_heap, slot->packet.hdr.seq_num);
}
}
}
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