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Bugfix: Send DNS replies from the same IP the request was sent to

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This commit is contained in:
Luke Dashjr 2012-06-03 17:10:46 +00:00
parent 7cccaba343
commit 4947772477
1 changed files with 73 additions and 9 deletions
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82
dns.c
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@ -1,3 +1,4 @@
#include <stdbool.h>
#include <stdio.h> #include <stdio.h>
#include <string.h> #include <string.h>
#include <stdlib.h> #include <stdlib.h>
@ -8,11 +9,35 @@
#include <arpa/inet.h> #include <arpa/inet.h>
#include <time.h> #include <time.h>
#include <ctype.h> #include <ctype.h>
#include <unistd.h>
#include "dns.h" #include "dns.h"
#define BUFLEN 512 #define BUFLEN 512
#if defined IP_RECVDSTADDR
# define DSTADDR_SOCKOPT IP_RECVDSTADDR
# define DSTADDR_DATASIZE (CMSG_SPACE(sizeof(struct in_addr)))
# define dstaddr(x) (CMSG_DATA(x))
#elif defined IP_PKTINFO
struct in_pktinfo {
unsigned int ipi_ifindex; /* Interface index */
struct in_addr ipi_spec_dst; /* Local address */
struct in_addr ipi_addr; /* Header Destination address */
};
# define DSTADDR_SOCKOPT IP_PKTINFO
# define DSTADDR_DATASIZE (CMSG_SPACE(sizeof(struct in_pktinfo)))
# define dstaddr(x) (&(((struct in_pktinfo *)(CMSG_DATA(x)))->ipi_addr))
#else
# error "can't determine socket option"
#endif
union control_data {
struct cmsghdr cmsg;
unsigned char data[DSTADDR_DATASIZE];
};
typedef enum { typedef enum {
CLASS_IN = 1, CLASS_IN = 1,
QCLASS_ANY = 255 QCLASS_ANY = 255
@ -348,12 +373,21 @@ int dnsserver(dns_opt_t *opt) {
if (senderSocket == -1) if (senderSocket == -1)
return -3; return -3;
int replySocket;
if (listenSocket == -1) { if (listenSocket == -1) {
struct sockaddr_in si_me; struct sockaddr_in si_me;
if ((listenSocket=socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP))==-1) { if ((listenSocket=socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP))==-1) {
listenSocket = -1; listenSocket = -1;
return -1; return -1;
} }
replySocket = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
if (replySocket == -1)
{
close(listenSocket);
return -1;
}
int sockopt = 1;
setsockopt(listenSocket, IPPROTO_IP, DSTADDR_SOCKOPT, &sockopt, sizeof sockopt);
memset((char *) &si_me, 0, sizeof(si_me)); memset((char *) &si_me, 0, sizeof(si_me));
si_me.sin_family = AF_INET; si_me.sin_family = AF_INET;
si_me.sin_port = htons(opt->port); si_me.sin_port = htons(opt->port);
@ -361,18 +395,48 @@ int dnsserver(dns_opt_t *opt) {
if (bind(listenSocket, (struct sockaddr*)&si_me, sizeof(si_me))==-1) if (bind(listenSocket, (struct sockaddr*)&si_me, sizeof(si_me))==-1)
return -2; return -2;
} }
unsigned char inbuf[BUFLEN], outbuf[BUFLEN]; unsigned char inbuf[BUFLEN], outbuf[BUFLEN];
do { struct iovec iov[1] = {
socklen_t si_other_len = sizeof(si_other); {
ssize_t insize = recvfrom(listenSocket, inbuf, BUFLEN, 0, (struct sockaddr*)&si_other, &si_other_len); .iov_base = inbuf,
.iov_len = sizeof(inbuf),
},
};
union control_data cmsg;
struct msghdr msg = {
.msg_name = &si_other,
.msg_namelen = sizeof(si_other),
.msg_iov = iov,
.msg_iovlen = 1,
.msg_control = &cmsg,
.msg_controllen = sizeof(cmsg),
};
for (; 1; ++(opt->nRequests))
{
ssize_t insize = recvmsg(listenSocket, &msg, 0);
unsigned char *addr = (unsigned char*)&si_other.sin_addr.s_addr; unsigned char *addr = (unsigned char*)&si_other.sin_addr.s_addr;
// printf("DNS: Request %llu from %i.%i.%i.%i:%i of %i bytes\n", (unsigned long long)(opt->nRequests), addr[0], addr[1], addr[2], addr[3], ntohs(si_other.sin_port), (int)insize); // printf("DNS: Request %llu from %i.%i.%i.%i:%i of %i bytes\n", (unsigned long long)(opt->nRequests), addr[0], addr[1], addr[2], addr[3], ntohs(si_other.sin_port), (int)insize);
opt->nRequests++; if (insize <= 0)
if (insize > 0) { continue;
ssize_t ret = dnshandle(opt, inbuf, insize, outbuf);
if (ret > 0) ssize_t ret = dnshandle(opt, inbuf, insize, outbuf);
sendto(listenSocket, outbuf, ret, 0, (struct sockaddr*)&si_other, sizeof(si_other)); if (ret <= 0)
continue;
bool handled = false;
for (struct cmsghdr*hdr = CMSG_FIRSTHDR(&msg); hdr; hdr = CMSG_NXTHDR(&msg, hdr))
{
if (hdr->cmsg_level == IPPROTO_IP && hdr->cmsg_type == DSTADDR_SOCKOPT)
{
msg.msg_iov[0].iov_base = outbuf;
sendmsg(listenSocket, &msg, 0);
msg.msg_iov[0].iov_base = inbuf;
handled = true;
}
} }
} while(1); if (!handled)
sendto(listenSocket, outbuf, ret, 0, (struct sockaddr*)&si_other, sizeof(si_other));
}
return 0; return 0;
} }