I have a basic task to connect some nodes to switch and let them communicate only with even-to-even and odd-to-odd IP addresses.
Scenario topology:
The starting point is an access network with full L2 connectivity based on a <DestMAC,OutputPort> table implemented on P4 switch.
Goal
Write a P4 code that creates two network slices, one enabling communication only between nodes with even IP addresses
and the other enabling communication only between nodes with odd IP addresses
header ipv4_t {
bit<4> version;
bit<4> ihl;
bit<8> diffserv;
bit<16> totalLen;
bit<16> identification;
bit<3> flags;
bit<13> fragOffset;
bit<8> ttl;
bit<8> protocol;
bit<16> hdrChecksum;
ip4Addr_t srcAddr;
ip4Addr_t dstAddr;
}
struct headers {
ethernet_t ethernet;
ipv4_t ipv4; //tay
}
/**SOME CODE*/
/*************************************************************************
************** I N G R E S S P R O C E S S I N G *******************
*************************************************************************/
control MyIngress(inout headers hdr,
inout metadata meta,
inout standard_metadata_t standard_metadata) {
action drop() {
mark_to_drop(standard_metadata);
}
action check_ip_odd_even(){
//TODO:
}
action forward_to_port(bit<9> egress_port) {
standard_metadata.egress_spec = egress_port;
}
table dmac_forward {
key = {
hdr.ethernet.dstAddr: exact;
}
actions = {
//ipv4_forward;
forward_to_port;
drop;
}
size = 8;
default_action = drop;
}
apply {
// if(hdr.ipv4.srcAddr & 1 == 1){
// //it's odd
// //dmac_forward.apply();
// }
// else {
// // it's even
// dmac_forward.apply();
// }
//10.0.0.13 vs 10.0.0.11
if (hdr.ipv4.srcAddr == 0x0a00000D && hdr.ipv4.dstAddr == 0x0a00000b){
dmac_forward.apply();
}
}
}
I tried to and with 1 so if it's 1 I would say it's odd but my solution didn't work. I also tried with exactly given IP addresses but this is not the general solution.
Any suggestion, please?
Related
I have a master device and ESP32 acting as a slave, communicating directly over UART with RX/TX cables. I've created a task that checks the serial stream every 50 ms and parses the data. My problem is that the serial stream freezes up, seemingly randomly, and only restarts if the master or the slave are restarted.
The task looks as such:
void TaskListen_UART(void *pvParameters)
{
while (true)
{
if (readSerialIn())
{
slaveRunCommand(serialData.command); // Execute received commmand
}
vTaskDelay(50 / portTICK_PERIOD_MS);
}
}
It checks the serial stream through readSerialIn() which looks like the following:
bool readSerialIn()
{
if (UART.available() > 0) // Check if the Serial port received data
{
serialData.clearStruct(); // Clear previously saved data
if (UART.find(0x2A)) // Find "*" // Find starting delimiter
{
serialData.length = UART.read(); // Read length
if (serialData.length > BYTE_BUFFER_LEN)
{
writeSerialNACK(); // Write NACK if length seems incorrect
return false;
}
Serial.printf(("Message length: %d\n"), serialData.length);
serialData.checksum = UART.read(); // Read Checksum
Serial.printf(("Checksum: %d\n"), serialData.checksum);
if (parseBuffer(serialData.length)) // Parse the data
{
if (serialData.checkSum()) // If the checksum passes
{
serialData.assignBuffer(); // Save the parsed data to the global buffer
return true;
}
else
{
writeSerialNACK();
return false;
}
}
else
false;
}
else
return false;
}
}
The parseBuffer() function is what actually reads the stream and parses it into their according values on the slave. I tried to write it in the most fail-safe fashion, but it still hasn't cleared up my issue.
bool parseBuffer(uint8_t bufferLength)
{
uint8_t bufferPos = 0;
bool uartDetectFlag = false;
while (UART.available() > 0)
{
uartDetectFlag = true;
if (bufferPos < bufferLength)
{
serialData.serialBuffer[bufferPos] = UART.read();
}
bufferPos++;
}
if (uartDetectFlag)
return true;
else
return false;
}
At first I was suspicious that the ESP was trying to access a block in memory that doesn't exist. I noticed however that it doesn't reset itself like it normally would if that were the case, and I tried writing parseBuffer in a non-blocking manner. I also tried increasing the task delay to 100 ms, which reduced the frequency of the blocking but did not suffice in terms of speed. Regardless, it freezes up and (I think) it's caused by a large flow of data through the serial stream.
I am trying to implement a TCP server using C in Linux. I want this server to accept incoming data forever from multiple clients and at the same time send some data back to each connected client in every 3 seconds.
My problem is I don't know how to properly do send() in a different process than the one handling the client.
What I am doing is at the beginning of the program do a fork() and do
while (1) {
sleep(3);
// compute and `send()` data to each connected peers
}
in child process, do
sock = create_socket();
while (1) {
client_sock = accept_connection(sock);
if (fork() == 0) {
close(sock);
handle_client(client_sock);
exit(0);
}
close(client_sock);
// clean up zombies
}
in parent process. handle_client() is simply recv() data in a infinite loop. Because send() and recv() are executed in different processes, I couldn't use the socket file descriptors to send() in parent process. What do I need to do in the parent process to do the send()?
You have three levels of processes, a parent, a child, and many grandchildren. Get rid of these levels, and do not fork at all; instead using an event-driven model in a single process.
In rough pseudo-code (translate to your preferred language):
listening_fd = create_socket();
EventQueueOfSomeKind q; // kqueue()-style
q.add_or_update_event(listening_fd, EVFILT_READ, EV_ENABLE);
q.add_or_update_event(3, EVFILT_TIMER, EV_ENABLE, NOTE_SECONDS);
FDToContextMapOfSomeKind context_map;
EventVector event_vector; // vector of kevent-like things
while (1) {
q.wait_for_events(&event_vector); // kevent()-style
foreach e <- event_vector {
switch (e.type) {
case EVFILT_READ:
if (listening_fd == e.fd) {
client_sock = accept_connection(e.fd, SOCK_NONBLOCK);
q.add_or_update_event(client_sock, EVFILT_READ, EV_ENABLE);
q.add_or_update_event(client_sock, EVFILT_WRITE, EV_DISABLE);
context_map.add_new_context(client_socket);
} else {
// Must be one of the client sockets
if (e.flags & EV_EOF) {
context_map.remove_context(e.fd);
q.remove_event(e.fd, EVFILT_READ);
q.remove_event(e.fd, EVFILT_WRITE);
close(e.fd);
} else {
recv(e.fd, buffer);
handle_client_input(&context_map[e.fd], buffer);
}
}
break;
case EVFILT_WRITE:
if (has_queued_output(context_map[e.fd])) {
send(e.fd, pull_queued_output(&context_map[e.fd]));
} else {
q.add_or_update_event(client_sock, EVFILT_WRITE, EV_DISABLE);
}
break;
case EVFILT_TIMER:
foreach client_sock,context <- context_map {
push_queued_output(&context, computed_data(context));
q.add_or_update_event(client_sock, EVFILT_WRITE, EV_ENABLE);
}
break;
}
}
}
I have glossed over partial send()s and recv()s, write-side shutdown, and all error handling but this is the general idea.
Further reading
https://github.com/mheily/libkqueue
Jonathan Lemon. kqueue. OpenBSD System Calls Manual.
Jonathan Lemon. kqueue. Darwin BSD Calls Manual. Apple corporation.
This is a solution using Linux epoll and timerfd (error handling is omitted):
int start_timer(unsigned int interval) {
int tfd;
struct itimerspec tspec;
tspec.it_value.tv_sec = 1;
tspec.it_value.tv_nsec = 0;
tspec.it_interval.tv_sec = 3;
tspec.it_interval.tv_nsec = 0;
tfd = timerfd_create(CLOCK_MONOTONIC, 0);
timerfd_settime(tfd, TFD_TIMER_ABSTIME, &tspec, NULL);
return tfd;
}
void epset_add(int epfd, int fd, uint32_t events)
{
struct epoll_event ev;
ev.data.fd = fd;
ev.events = events;
epoll_ctl(epfd, EPOLL_CTL_ADD, fd, &ev);
}
int main()
{
int epfd, tfd, sock, nfds, i;
struct epoll_event events[MAX_EVENTS];
/* create new epoll instance */
epfd = epoll_create1(0);
tfd = start_timer(TIMER_INTERVAL);
/* socket(), bind() and listen() omitted in create_socket() */
sock = create_socket(PORT_NUMBER);
/* add sock and tfd to epoll set */
epset_add(epfd, tfd, EPOLLIN);
epset_add(epfd, sock, EPOLLIN | EPOLLET);
for (;;) {
for (i = 0; i < nfds; ++i) {
if (events[i].data.fd == tfd) {
/* handle timer notification, it's run
periodically with interval TIMER_INTERVAL */
} else if (events[i].data.fd == sock) {
/* accept() incoming connections,
set non-blocking,
and add new connection sockets to epoll set */
} else {
/* recv() from connection sockets and handle */
}
}
}
}
This program was helpful https://github.com/eklitzke/epollet/blob/master/poll.c and I added timerfd to the epoll set so the server keeps listening and receiving data and at the same time can send data to the clients periodically.
I am trying to modify the multihop Oscilloscope program so that the sink node is able to send data both to UART and radio medium as well. As far as researched, I found out that the same hardware is used for sending packets via UART and radio too.
In this case, how do I modify my code so that I can send data to UART or radio based on a condition I receive. Here in the sample prorgram, I send data via radio on every 10 packets received.
The receive module for my sink node is:
event message_t* Receive.receive(message_t* msg, void *payload, uint8_t len) {
oscilloscope_t* in = (oscilloscope_t*)payload;
counter++;
am_addr_t rec = call AMPacket.source(msg);
oscilloscope_t* out;
counter++;
call Leds.led0On();
if (uartbusy == FALSE) {
out = (oscilloscope_t*)call SerialSend.getPayload(&uartbuf, sizeof(oscilloscope_t));
if (len != sizeof(oscilloscope_t) || out == NULL) {
return msg;
}
else {
memcpy(out, in, sizeof(oscilloscope_t));
}
uartlen = sizeof(oscilloscope_t);
post uartSendTask();
} else {
message_t *newmsg = call UARTMessagePool.get();
if (newmsg == NULL) {
report_problem();
return msg;
}
//Serial port busy, so enqueue.
out = (oscilloscope_t*)call SerialSend.getPayload(newmsg, sizeof(oscilloscope_t));
if (out == NULL) {
return msg;
}
memcpy(out, in, sizeof(oscilloscope_t));
if (call UARTQueue.enqueue(newmsg) != SUCCESS) {
call UARTMessagePool.put(newmsg);
fatal_problem();
return msg;
}
}
if(counter % 10 == 0){
oscilloscope_t* btrpkt = (oscilloscope_t*)(call Packet.getPayload(&pkt, sizeof(oscilloscope_t)));
call Leds.led1On();
if (call AMSend.send(rec, &pkt, sizeof(oscilloscope_t)) == SUCCESS) {
call Leds.led0On();
sendbusy = TRUE;
}
}
return msg;
}
Once the data sends back to the node from where it received the packet , it is unable to process it through UART again. Could anyone help me how could I solve my problem?
According to the question and comments:
You must instantiate AMSenderC with the same id as for the receiver. In this case, AM_OSCILLOSCOPE if you want a message to be processed by the same code. Or another id plus a new implementation of the Receive interface.
You missed putting payload into btrpkt.
You must check for sendbusy - it is a bug if you try to use the radio stack when it is busy.
I have implemented a protocol named TRLR for wireless networks which is not an ad-hoc routing protocol. It just allows nodes to send R_UPDATE message after some specified time. Everything is running smooth but TCP source only communicates with the TCPSINK when they are in each other's range. I want to send these packets through multi-hop by the shortest route possible. How to do it in ns-2.34?
Please help.
forward function of my protocol.
void
TRLR::forward(RouteEntry* rt, Packet *p, double delay)
{
struct hdr_cmn *ch = HDR_CMN(p);
struct hdr_ip *ih = HDR_IP(p);
if(ih->ttl_ == 0) {
#ifdef DEBUG
fprintf(stderr, "%s: calling drop()\n", __PRETTY_FUNCTION__);
#endif // DEBUG
drop(p, DROP_RTR_TTL);
return;
}
if (ch->ptype() != PT_TRLR && ch->direction() == hdr_cmn::UP &&
((u_int32_t)ih->daddr() == IP_BROADCAST)
|| (ih->daddr() == here_.addr_)) {
dmux_->recv(p,0);
return;
}
if (rt) {
assert(rt->rt_flags == RTF_UP);
rt->rt_expire = CURRENT_TIME + ACTIVE_ROUTE_TIMEOUT;
ch->next_hop_ = rt->rt_nexthop;
ch->addr_type() = NS_AF_INET;
ch->direction() = hdr_cmn::DOWN; //important: change the packet's direction
}
else { // if it is a broadcast packet
assert(ih->daddr() == (nsaddr_t) IP_BROADCAST);
ch->addr_type() = NS_AF_NONE;
ch->direction() = hdr_cmn::DOWN; //important: change the packet's direction
}
if (ih->daddr() == (nsaddr_t) IP_BROADCAST) {
// If it is a broadcast packet
if (ch->ptype() != PT_TRLR) {
Scheduler::instance().schedule(target_, p, 0.);
}
}
else { // Not a broadcast packet
if(delay > 0.0) {
Scheduler::instance().schedule(target_, p, delay);
}
else {
// Not a broadcast packet, no delay, send immediately
Scheduler::instance().schedule(target_, p, 0.);
}
}
}
I've been trying to modify the tcp server example with LwIP in STM32F4DISCOVERY board. I have to write a sender which does not necessarily have to reply server responses. It can send data with 100 ms frequency, for example.
Firstly, the example of TCP server is like this:
static void tcpecho_thread(void *arg)
{
struct netconn *conn, *newconn;
err_t err;
LWIP_UNUSED_ARG(arg);
/* Create a new connection identifier. */
conn = netconn_new(NETCONN_TCP);
if (conn!=NULL) {
/* Bind connection to well known port number 7. */
err = netconn_bind(conn, NULL, DEST_PORT);
if (err == ERR_OK) {
/* Tell connection to go into listening mode. */
netconn_listen(conn);
while (1) {
/* Grab new connection. */
newconn = netconn_accept(conn);
/* Process the new connection. */
if (newconn) {
struct netbuf *buf;
void *data;
u16_t len;
while ((buf = netconn_recv(newconn)) != NULL) {
do {
netbuf_data(buf, &data, &len);
//Incoming package
.....
//Check for data
if (DATA IS CORRECT)
{
//Reply
data = "OK";
len = 2;
netconn_write(newconn, data, len, NETCONN_COPY);
}
} while (netbuf_next(buf) >= 0);
netbuf_delete(buf);
}
/* Close connection and discard connection identifier. */
netconn_close(newconn);
netconn_delete(newconn);
}
}
} else {
printf(" can not bind TCP netconn");
}
} else {
printf("can not create TCP netconn");
}
}
I modified this code to obtain a client version, this is what I've got so far:
static void tcpecho_thread(void *arg)
{
struct netconn *xNetConn = NULL;
struct ip_addr local_ip;
struct ip_addr remote_ip;
int rc1, rc2;
struct netbuf *Gonderilen_Buf = NULL;
struct netbuf *gonderilen_buf = NULL;
void *b_data;
u16_t b_len;
IP4_ADDR( &local_ip, IP_ADDR0, IP_ADDR1, IP_ADDR2, IP_ADDR3 );
IP4_ADDR( &remote_ip, DEST_IP_ADDR0, DEST_IP_ADDR1, DEST_IP_ADDR2, DEST_IP_ADDR3 );
xNetConn = netconn_new ( NETCONN_TCP );
rc1 = netconn_bind ( xNetConn, &local_ip, DEST_PORT );
rc2 = netconn_connect ( xNetConn, &remote_ip, DEST_PORT );
b_data = "+24C"; // Data to be send
b_len = sizeof ( b_data );
while(1)
{
if ( rc1 == ERR_OK )
{
// If button pressed, send data "+24C" to server
if (GPIO_ReadInputDataBit (GPIOA, GPIO_Pin_0) == Bit_SET)
{
Buf = netbuf_new();
netbuf_alloc(Buf, 4); // 4 bytes of buffer
Buf->p->payload = "+24C";
Buf->p->len = 4;
netconn_write(xNetConn, Buf->p->payload, b_len, NETCONN_COPY);
vTaskDelay(100); // To see the result easily in Comm Operator
netbuf_delete(Buf);
}
}
if ( rc1 != ERR_OK || rc2 != ERR_OK )
{
netconn_delete ( xNetConn );
}
}
}
While the writing operation works, netconn_write sends what's on its buffer. It doesnt care whether b_data is NULL or not. I've tested it by adding the line b_data = NULL;
So the resulting output in Comm Operator is like this:
Rec:(02:47:27)+24C+24C+24C+24C+24C+24C+24C+24C+24C+24C+24C+24C+24C+24C+24C+24C+24C+24C+24C+24C+24C+24C+24C+24C+24C+24C+24C+24C+24C+24C+24C+24C+24C
However, I want it to work like this:
Rec:(02:47:22)+24C
Rec:(02:47:27)+24C
Rec:(02:57:12)+24C
Rec:(02:58:41)+24C
The desired write operation happens when I wait for around 8 seconds before I push the button again.
Since netconn_write function does not allow writing to a buffer, I'm not able to clear it. And netconn_send is only allowed for UDP connections.
I need some guidance to understand the problem and to generate a solution for it.
Any help will be greately appreciated.
It's just a matter of printing the result in the correct way.
You can try to add this part of code before writing in the netbuf data structure:
char buffer[20];
sprintf(buffer,"24+ \n");
Buf->p->payload = "+24C";
I see one or two problems in your code, depending on what you want it exactly to do. First of all, you're not sending b_data at all, but a constant string:
b_data = "+24C"; // Data to be send
and then
Buf->p->payload = "+24C";
Buf->p->len = 4;
netconn_write(xNetConn, Buf->p->payload, b_len, NETCONN_COPY);
b_data is not anywhere mentioned there. What is sent is the payload. Try Buf->p->payload = b_data; if it's what you want to achieve.
Second, if you want the +24C text to be sent only once when you push the button, you'll have to have a loop to wait for the button to open again before continuing the loop, or it will send +24C continuously until you stop pushing the button. Something in this direction:
while (GPIO_ReadInputDataBit (GPIOA, GPIO_Pin_0) == Bit_SET) {
vTaskDelay(1);
}