I have two network links to the Internet, and I have two default routes set up:
Destination Gateway Genmask Flags Metric Ref Use Iface
default gateway0 0.0.0.0 UG 0 0 eth0
default gateway1 0.0.0.0 UG 0 0 eth1
...
I created two sockets with BINDTODEVICE, so that I can send data out either eth0 or eth1. I am also trying to listen on both sockets using recvfrom (UDP data only), but I can only successfully read data from whichever interface is listed first in the routes. eth0 works, for example, but I get nothing from the socket bound to eth1.
Running wireshark on either interface shows data coming in successfully - that is, I can see data being sent from the Internet to either eth0's or eth1's IP in Wireshark (so NAT is not a problem with either), but my program just blocks on recvfrom without getting any data.
I have tried using bind on the sockets to make them listen on their respective interface's IP, and also tried not using bind to have them listen on 0.0.0.0 (each on a different port), but I still have the same problem.
How can I make sure both sockets get the data they're supposed to?
Edit: sample code:
int createDeviceBoundUDPSocket(uint32_t sip, uint16_t sport, const char* bind_dev) {
printf("bind_dev = %s", bind_dev);
int s = socket(AF_INET, SOCK_DGRAM, 0);
int result;
struct sockaddr_in my_ip_addr;
if (s < 0) {
perror("socket");
return s;
}
memset(&my_ip_addr, 0, sizeof(my_ip_addr));
my_ip_addr.sin_family = AF_INET;
my_ip_addr.sin_addr.s_addr = htonl(sip);
my_ip_addr.sin_port = htons(sport);
// commenting this section out doesn't seem to make a difference
// listening on 0.0.0.0 or the interface's IP both have the same problem
result = bind(s, (struct sockaddr*)(&my_ip_addr), sizeof(my_ip_addr));
if (result < 0) {
perror("Error in bind");
return result;
}
if (bind_dev) {
// Bind to specific device.
if (setsockopt(s, SOL_SOCKET, SO_BINDTODEVICE,
bind_dev, strlen(bind_dev) + 1)) {
perror("Error binding to device");
return -1;
}
}
return s;
}
The solution, as hinted by the Linux Advanced Routing and Traffic Control guide, is to turn off reverse path filtering. Not sure which of the three interfaces needed to have it turned off, but doing
echo 0 > /proc/sys/net/ipv4/conf/all/rp_filter
made it work.
Related
I'm developing device base on ESP32 module that have a UDP socket open only to receive broadcast packets on one port (7890 to be exact). The problem is that the data losses are high - around 90%. My test setup is:
ESP32 - connected to WiFi network with open UDP receing task (code belowe)
PC connected to the same netwer via LAN with UDP terminal set to brodacast to remote: 192.168.10.255:7890
Mobile phone connected to WiFi with UDP terminal set to brodacast to remote: 192.168.10.255:7890
When I send something from PC or mobile phone there is no data lossage between Mobile phone and PC but ESP32 receive around 10% of data that I transmit from both of senders. If I change from multicast to unicast on PC or Phone to send data to ESP32, it work without problem.
I know that UDP does not guarantee the delivery but 10% efficiency seems for me to be super low, especially when it seems that there is no problem with busy network because PC and mobile received the data all the time.
Do you have any suggestion to the code or some setting that can be changed in menu config ?
At the moment my application have only two tasks:
WiFi Task that after connection is just waiting for event
UDP Task that the code is below
Update 04.07.2018 (13:15)
Problem disappear when I don't initialize bluetooth. Sorry that I didn't mention previously about BT being initialized but I kept me initializing function from my normal program that have a lot more tasks (BT included) and totally forgot about this myself.
Anyway - do you think that there is some issue with sharing the resource or is it some physical interference ? I'm using ESP32-DevKitC that is on the breadboard, so no additional shielding is present.
#define PORT_NUMBER 7890
#define BUFLEN 100
void udp_task(void *pvParameter)
{
struct sockaddr_in clientAddress;
struct sockaddr_in serverAddress;
struct sockaddr_in si_other;
unsigned int slen = sizeof(si_other);
unsigned int recv_len;
char buf[BUFLEN];
int sock;
printf("UDP Task: Opening..\n");
int ret;
ret = UDP_List_Open(&clientAddress, &serverAddress, &sock);
if(ret == 0)
{
printf("UDP Task: Open\n");
}
else
{
printf("UDP Task: Can't open\n");
}
while(1)
{
memset(buf,0,100);
if ((recv_len = recvfrom(sock, buf, 100, 0, (struct sockaddr *) &si_other, &slen)) == -1)
{
printf("UDP error\n");
break;
}
sendto(sock, buf, recv_len, 0, (struct sockaddr *)&si_other, sizeof(si_other));
printf("UDP Task: Received packet from %s:%d\n", inet_ntoa(si_other.sin_addr), ntohs(si_other.sin_port));
printf("UDP Task: Data: %s -- %d\n" , buf, recv_len);
}
while(1)
{
vTaskDelay(100 / portTICK_RATE_MS);
}
}
int UDP_List_Open(struct sockaddr_in* clientAddress, struct sockaddr_in* serverAddress, int* sock)
{
// Create a socket that we will listen upon.
*sock = socket(AF_INET, SOCK_DGRAM, 0);
if (*sock < 0)
{
printf("UDP List Open: Socket error\n");
return 1;
}
// Bind our server socket to a port.
serverAddress->sin_family = AF_INET;
serverAddress->sin_addr.s_addr = htonl(INADDR_ANY);
serverAddress->sin_port = htons(PORT_NUMBER);
int rc = bind(*sock, serverAddress, sizeof(*serverAddress));
if (rc < 0)
{
printf("UDP List Open: Bind error\n");
return 2;
}
return 0;
}
Even though UDP is considered fire and forget, (unlike TCP), unicast UDP through WiFi is reliable because reliability is built into the WiFi protocol. But this can work for Unicast only because there is one known recipient. Multicast UDP is unreliable because there are no checks and retries.
I had the same problem when I was trying to use multicast UDP with the ESP8266. It caused me to dig deeper into the issue. In the end I use UDP multicast for discovery but then switch to Unicast UDP for subsequent transfers.
See Multicast Wifi Problem Statement
https://tools.ietf.org/id/draft-mcbride-mboned-wifi-mcast-problem-statement-01.html
I need to inspect and modify the IPv6 extension headers. So I set up a raw socket to listen for all IP packets on the local address.
package main
import (
"log"
"net"
)
func main() {
c, err := net.ListenIP("ip6:tcp", &net.IPAddr{
IP: net.IPv6loopback,
Zone: "",
})
if err != nil {
panic(err)
}
buf := make([]byte, 1024)
for {
numRead, ipaddr, err := c.ReadFromIP(buf)
log.Print(numRead, ipaddr, err)
log.Printf("% X\n", buf[:numRead])
}
}
I tried all the Read*() methods on the connection but it seems like they just return the payload without the header.
So my question is: How can I access the IPv6 header of a packet?
Raw sockets with IPv6 are different compared to IPv4. Relevant for your case is RFC 3542. Note:
Another difference from IPv4 raw sockets is that complete packets (that is, IPv6 packets with extension headers) cannot be sent or received using the IPv6 raw sockets API. Instead, ancillary data objects are used to transfer the extension headers and hoplimit information, as described in Section 6. Should an application need access to the complete IPv6 packet, some other technique, such as the datalink interfaces BPF or DLPI, must be used.
You can find this out on your own. By running (and strace'ing) your program on my box for every packet I get:
recvfrom(3, "\x45\x00\x00\x3c\x6a\x7d...
^^
This means IP version = 4, IHL = 5 (20 bytes).
When I try the same thing with IPv6 (i.e. your original code), I get something different every time:
recvfrom(3, "\xc6\x22\x00\x50\x4d
In this case every time the kernel is returning stuff starting directly with TCP (in this case the port is 50722, i.e 0xC622).
Another interesting part should be noted in the sources:
switch sa := sa.(type) {
case *syscall.SockaddrInet4:
addr = &IPAddr{IP: sa.Addr[0:]}
n = stripIPv4Header(n, b)
case *syscall.SockaddrInet6:
addr = &IPAddr{IP: sa.Addr[0:], Zone: zoneToString(int(sa.ZoneId))}
}
The header is stripped manually for IPv4 but not for IPv6: for IPv6 there is nothing to remove.
Note, there are mechanisms that will return extra information (but by no means the whole packet). For example the IPV6_RECVPKTINFO socket option will give you access to:
struct in6_pktinfo {
struct in6_addr ipi6_addr; /* src/dst IPv6 address */
unsigned int ipi6_ifindex; /* send/recv interface index */
};
Similar options exist for the routing header option, hop limit etc.
I am trying to set up a socket to receive multicast UDP packets on VxWorks 6.8.
sin.sin_len = (u_char)sizeof (sin);
sin.sin_family = AF_INET;
sin.sin_addr.s_addr = INADDR_ANY;
/* UDP port number to match for the received packets */
sin.sin_port = htons (mcastPort);
/* bind a port number to the socket */
if (bind(sockDesc, (struct sockaddr *)&sin, sizeof(sin)) != 0)
{
perror("bind");
status = errno;
goto cleanUp;
}
/* fill in the argument structure to join the multicast group */
/* initialize the multicast address to join */
ipMreq.imr_multiaddr.s_addr = inet_addr (mcastAddr);
/* unicast interface addr from which to receive the multicast packets */
ipMreq.imr_interface.s_addr = inet_addr (ifAddr);
printf ("Interface address on which to receive multicast packets: %s\n", ifAddr);
/* set the socket option to join the MULTICAST group */
int code = setsockopt (sockDesc, IPPROTO_IP, IP_ADD_MEMBERSHIP,
(char *)&ipMreq,
sizeof (ipMreq));
The setsockopt() call is returning -1 and errno is being set to 49 or EADDRNOTAVAIL. On wireshark, when we perform setsockopt I can see a properly formed group unsubscribe packet being sent out from the right port/interface. All different combinations of interfaces, ports, and multicast groups give the same result.
I am unable to debug very far into setsockopt as there doesnt seem to be anything wrong before the task calls ipcom_pipe_send and ipnet_usr_sock_pipe_recv, and after the recv call errno is set. I dont know how to debug the relevant tNetTask code that may be generating the error.
It could be that there's an issue with the interface index you supplied. Define ipMreq to be a struct ip_mreq, which does not have the imr_ifindex, instead of a struct ip_mreqn and remove the ipMreq.imr_ifindex = 2; line.
I am trying to do the following:
Let us say I start a TCPServer on machine X. Now, I want to connect to the TCPServer from machine Y, but I want to specify the ports (both sender and receiver), on which the data communication should take place. Also, the TCPServer handles multiple clients at the same time.
MachineX: ./TCPServer
MachineY: ./TCPClient -SP 5000 -DP 5000
I have written the code for a multithreaded server (using C UNIX), and it works fine. Basically, it spawns one thread per connection. But I am not sure how to include the above functionality.
Thank you for your time!
Prior to calling connect(), call bind().
I'm assuming you had to do this for the server code, right? Otherwise, how do you get your server (running on MachineX) to listen on port 5000.
In any case, here's a C example of binding to localhost port 5000.
Example:
int sock = socket(AF_INET, SOCK_STREAM, 0);
sockaddr_in addrRemote = {};
sockaddr_in addrLocal = {}; // zero init so that sin_addr is already INADDR_ANY;
int result;
addrLocal.sin_family = AF_INET;
addrLocal.sin_port = htons(5000);
result = bind(sock, (sockaddr*)&addrLocal, sizeof(addrLocal));
if (result < 0)
return;
addrRemote.sin_family = AF_INET;
addrRemote.sin_port = htons(5000);
addrRemote.sin_addr = <ip of MachineX in network byte order>;
result = connect(sock, (sockaddr*)&addrRemote, sizeof(addrRemote));
if (result < 0)
return;
It's assumed that TCPServer running on machine X is listening on port 5000.
I'm writing simple program to communicate between smart devices and I receive 11001 when calling gethostbyaddr(). Both devices show they are connected to the same network, but from msdn document 11001 error is Host not found. No such host is known. Does anybody have any suggestion, thanks? My code is below.
void InitializeSocket()
{
WORD socketVersion;
WSADATA wsaData;
SOCKADDR_IN serverInfo;
int returnVal;
LPHOSTENT remotHost;
socketVersion = MAKEWORD(2,2);
WSAStartup(socketVersion, &wsaData);
in_addr iaHost;
//iaHost.s_addr = inet_addr("120.15.22.14");
iaHost.S_un.S_un_b.s_b1 = 120;
iaHost.S_un.S_un_b.s_b2 = 15;
iaHost.S_un.S_un_b.s_b3 = 22;
iaHost.S_un.S_un_b.s_b4 = 14;
remotHost = gethostbyaddr((const char *)&iaHost, sizeof(struct in_addr),
AF_INET);
if(iaHost.s_addr == INADDR_NONE)
{
MessageBox(NULL, TEXT("inet_addr has invalid address"),
TEXT("inet_addr"), MB_OK);
WSACleanup();
closesocket(theSocket);
return;
}
if(!remotHost)
{
returnVal = WSAGetLastError();
WSACleanup();
closesocket(theSocket);
return;
}
theSocket = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
if(theSocket == INVALID_SOCKET)
{
returnVal = WSAGetLastError();
WSACleanup();
closesocket(theSocket);
return;
}
serverInfo.sin_family = AF_INET;
serverInfo.sin_addr = *((LPIN_ADDR)*remotHost->h_addr_list);
serverInfo.sin_port = htons(8888);
//Connect to the server
returnVal = connect(theSocket, (LPSOCKADDR)&serverInfo,
sizeof(struct sockaddr));
if(returnVal == SOCKET_ERROR)
{
returnVal = WSAGetLastError();
WSACleanup();
closesocket(theSocket);
return;
}
}
Error 11001 is a generic DNS lookup error so I have only one question. Does the 120.15.22.14 address actually exist in DNS?
You can find this out by typing
nslookup 120.15.22.14
from the command line.
If you get an error, it's because DNS doesn't know anything about those addresses, so a gethostbyaddr() will not be able to give you any information.
Update:
Answering your points:
I just type nslookup 120.15.22.14, but it returns back as cant find 120.15.22.14. Non-existent domain.
Since nslookup 120.15.22.14 returns an error, there is no entry in DNS for that IP address. That's your problem.
I look at my device settings for the DNS and it sets to 120.20.32.10 which is different 120.15.22.14 so does it mean I haven't configured the DNS?
If 120.20.32.10 is what's in DNS for your device, and 120.15.22.14 is the actual address, then DNS is wrong. Plain and simple. Fix DNS.
will it produce the same result if I use gethostbyname() instead of gethostbyaddr()?
If you want to turn a DNS name into an IP address, use gethostbyname(). To turn an IP address into a DNS name, use gethostbyaddr().
For connecting to a remote host, you would normally use the gethostbyname() call since the IP address of the host could change at any time. Provided DNS always accurately represents the IP address of that host, that's the preferred way.
I just type nslookup 120.15.22.14, but it returns back as cant find 120.15.22.14. Non-existent domain.
I look at my device settings for the DNS and it sets to 120.20.32.10 which is different 120.15.22.14 so does it mean I haven't configured the DNS?