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/* dnsmasq is Copyright (c) 2000-2021 Simon Kelley
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; version 2 dated June, 1991, or
(at your option) version 3 dated 29 June, 2007.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include "dnsmasq.h"
#ifdef HAVE_DUMPFILE
static u32 packet_count;
/* https://wiki.wireshark.org/Development/LibpcapFileFormat */
struct pcap_hdr_s {
u32 magic_number; /* magic number */
u16 version_major; /* major version number */
u16 version_minor; /* minor version number */
u32 thiszone; /* GMT to local correction */
u32 sigfigs; /* accuracy of timestamps */
u32 snaplen; /* max length of captured packets, in octets */
u32 network; /* data link type */
};
struct pcaprec_hdr_s {
u32 ts_sec; /* timestamp seconds */
u32 ts_usec; /* timestamp microseconds */
u32 incl_len; /* number of octets of packet saved in file */
u32 orig_len; /* actual length of packet */
};
void dump_init(void)
{
struct stat buf;
struct pcap_hdr_s header;
struct pcaprec_hdr_s pcap_header;
packet_count = 0;
if (stat(daemon->dump_file, &buf) == -1)
{
/* doesn't exist, create and add header */
header.magic_number = 0xa1b2c3d4;
header.version_major = 2;
header.version_minor = 4;
header.thiszone = 0;
header.sigfigs = 0;
header.snaplen = daemon->edns_pktsz + 200; /* slop for IP/UDP headers */
header.network = 101; /* DLT_RAW http://www.tcpdump.org/linktypes.html */
if (errno != ENOENT ||
(daemon->dumpfd = creat(daemon->dump_file, S_IRUSR | S_IWUSR)) == -1 ||
!read_write(daemon->dumpfd, (void *)&header, sizeof(header), 0))
die(_("cannot create %s: %s"), daemon->dump_file, EC_FILE);
}
else if ((daemon->dumpfd = open(daemon->dump_file, O_APPEND | O_RDWR)) == -1 ||
!read_write(daemon->dumpfd, (void *)&header, sizeof(header), 1))
die(_("cannot access %s: %s"), daemon->dump_file, EC_FILE);
else if (header.magic_number != 0xa1b2c3d4)
die(_("bad header in %s"), daemon->dump_file, EC_FILE);
else
{
/* count existing records */
while (read_write(daemon->dumpfd, (void *)&pcap_header, sizeof(pcap_header), 1))
{
lseek(daemon->dumpfd, pcap_header.incl_len, SEEK_CUR);
packet_count++;
}
}
}
void dump_packet(int mask, void *packet, size_t len, union mysockaddr *src, union mysockaddr *dst)
{
struct ip ip;
struct ip6_hdr ip6;
int family;
struct udphdr {
u16 uh_sport; /* source port */
u16 uh_dport; /* destination port */
u16 uh_ulen; /* udp length */
u16 uh_sum; /* udp checksum */
} udp;
struct pcaprec_hdr_s pcap_header;
struct timeval time;
u32 i, sum;
void *iphdr;
size_t ipsz;
int rc;
if (daemon->dumpfd == -1 || !(mask & daemon->dump_mask))
return;
/* So wireshark can Id the packet. */
udp.uh_sport = udp.uh_dport = htons(NAMESERVER_PORT);
if (src)
family = src->sa.sa_family;
else
family = dst->sa.sa_family;
if (family == AF_INET6)
{
iphdr = &ip6;
ipsz = sizeof(ip6);
memset(&ip6, 0, sizeof(ip6));
ip6.ip6_vfc = 6 << 4;
ip6.ip6_plen = htons(sizeof(struct udphdr) + len);
ip6.ip6_nxt = IPPROTO_UDP;
ip6.ip6_hops = 64;
if (src)
{
memcpy(&ip6.ip6_src, &src->in6.sin6_addr, IN6ADDRSZ);
udp.uh_sport = src->in6.sin6_port;
}
if (dst)
{
memcpy(&ip6.ip6_dst, &dst->in6.sin6_addr, IN6ADDRSZ);
udp.uh_dport = dst->in6.sin6_port;
}
/* start UDP checksum */
for (sum = 0, i = 0; i < IN6ADDRSZ; i+=2)
{
sum += ip6.ip6_src.s6_addr[i] + (ip6.ip6_src.s6_addr[i+1] << 8) ;
sum += ip6.ip6_dst.s6_addr[i] + (ip6.ip6_dst.s6_addr[i+1] << 8) ;
}
}
else
{
iphdr = &ip;
ipsz = sizeof(ip);
memset(&ip, 0, sizeof(ip));
ip.ip_v = IPVERSION;
ip.ip_hl = sizeof(struct ip) / 4;
ip.ip_len = htons(sizeof(struct ip) + sizeof(struct udphdr) + len);
ip.ip_ttl = IPDEFTTL;
ip.ip_p = IPPROTO_UDP;
if (src)
{
ip.ip_src = src->in.sin_addr;
udp.uh_sport = src->in.sin_port;
}
if (dst)
{
ip.ip_dst = dst->in.sin_addr;
udp.uh_dport = dst->in.sin_port;
}
ip.ip_sum = 0;
for (sum = 0, i = 0; i < sizeof(struct ip) / 2; i++)
sum += ((u16 *)&ip)[i];
while (sum >> 16)
sum = (sum & 0xffff) + (sum >> 16);
ip.ip_sum = (sum == 0xffff) ? sum : ~sum;
/* start UDP checksum */
sum = ip.ip_src.s_addr & 0xffff;
sum += (ip.ip_src.s_addr >> 16) & 0xffff;
sum += ip.ip_dst.s_addr & 0xffff;
sum += (ip.ip_dst.s_addr >> 16) & 0xffff;
}
if (len & 1)
((unsigned char *)packet)[len] = 0; /* for checksum, in case length is odd. */
udp.uh_sum = 0;
udp.uh_ulen = htons(sizeof(struct udphdr) + len);
sum += htons(IPPROTO_UDP);
sum += htons(sizeof(struct udphdr) + len);
for (i = 0; i < sizeof(struct udphdr)/2; i++)
sum += ((u16 *)&udp)[i];
for (i = 0; i < (len + 1) / 2; i++)
sum += ((u16 *)packet)[i];
while (sum >> 16)
sum = (sum & 0xffff) + (sum >> 16);
udp.uh_sum = (sum == 0xffff) ? sum : ~sum;
rc = gettimeofday(&time, NULL);
pcap_header.ts_sec = time.tv_sec;
pcap_header.ts_usec = time.tv_usec;
pcap_header.incl_len = pcap_header.orig_len = ipsz + sizeof(udp) + len;
if (rc == -1 ||
!read_write(daemon->dumpfd, (void *)&pcap_header, sizeof(pcap_header), 0) ||
!read_write(daemon->dumpfd, iphdr, ipsz, 0) ||
!read_write(daemon->dumpfd, (void *)&udp, sizeof(udp), 0) ||
!read_write(daemon->dumpfd, (void *)packet, len, 0))
my_syslog(LOG_ERR, _("failed to write packet dump"));
else
my_syslog(LOG_INFO, _("dumping UDP packet %u mask 0x%04x"), ++packet_count, mask);
}
#endif
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