rnhmjoj/fakeroute
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Get the actual local address, not 0.0.0.0

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The sockets are bound on all interfaces using INADDR_ANY, so getsockname
always return 0.0.0.0.
The actual address can be obtained from the destination address of the
received IP packet using the socket ancillary data.
This commit is contained in:
Michele Guerini Rocco 2023-06-17 10:41:10 +02:00
parent c7f3f9df4e
commit 940af5a896
Signed by: rnhmjoj
GPG Key ID: BFBAF4C975F76450
2 changed files with 27 additions and 6 deletions
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3
src/TracerouteListener.cpp
View File

@ -77,6 +77,9 @@ int TracerouteListener::bindSocket(int port) {
localAddress.sin_addr.s_addr = INADDR_ANY;
localAddress.sin_port = htons(port);
int on = 1;
setsockopt(sockfd, IPPROTO_IP, IP_PKTINFO, &on, sizeof(on));
if ((bind(sockfd, (struct sockaddr*)&localAddress, sizeof(localAddress))) < 0) {
fprintf(stderr, "Error Binding Socket\n");
exit(1);

30
src/TracerouteReader.cpp
View File

@ -38,24 +38,42 @@
#include <stdlib.h>
class TraceroutePacket* TracerouteReader::readPacket(int fd) {
char packet[32*1024];
char cmsg[CMSG_SPACE(sizeof(struct in_pktinfo))];
struct sockaddr_in remoteAddress;
struct sockaddr_in localAddress;
struct msghdr msg;
unsigned int size = sizeof(remoteAddress);
memset((void*)&remoteAddress, 0, size);
memset((void*)&localAddress, 0, size);
memset((void*)&msg, 0, sizeof(msg));
if ((recvfrom(fd, packet, 32*1024, 0, (struct sockaddr*)&remoteAddress, &size)) < 0) {
// get local address
if ((getsockname(fd, (struct sockaddr*)&localAddress, &size)) < 0) {
fprintf(stderr, "Error getting local name.");
exit(1);
}
// read message
msg.msg_name = &remoteAddress;
msg.msg_namelen = size;
msg.msg_control = &cmsg;
msg.msg_controllen = sizeof(cmsg);
if (recvmsg(fd, &msg, 0) < 0) {
fprintf(stderr, "Error receiving datagram.");
exit(1);
}
if ((getsockname(fd, (struct sockaddr*)&localAddress, &size)) < 0) {
fprintf(stderr, "Error getting local name.");
exit(1);
// get actual IP address
for (struct cmsghdr *cmsg = CMSG_FIRSTHDR(&msg);
cmsg != NULL;
cmsg = CMSG_NXTHDR(&msg, cmsg)) {
if (cmsg->cmsg_level == IPPROTO_IP && cmsg->cmsg_type == IP_PKTINFO) {
struct in_pktinfo *pi = (struct in_pktinfo *) CMSG_DATA(cmsg);
localAddress.sin_addr = pi->ipi_spec_dst;
break;
}
}
return new TraceroutePacket(inet_ntoa(remoteAddress.sin_addr),