Pi-Hole/dnsmasq
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Make the packet-dump code work with a FIFO.

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mkfifo /tmp/dnsmasq.pipe
dnsmasq --dumpfile=/tmp/dnsmasq.pipe ....
wireshark -i /tmp/dnsmasq.pipe

gives real-time display of network traffic in Wireshark.
This commit is contained in:
Simon Kelley
2024-11-27 16:03:13 +00:00
parent c6bc22adc7
commit 41d2ae3203
2 changed files with 17 additions and 9 deletions
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2
man/dnsmasq.8
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@@ -781,7 +781,7 @@ The address range can be of the form
must fall in the same /64 network, or prefix-length must be greater than or equal to 64 except that shorter prefix lengths than 64 are allowed only if non-sequential names are in use. must fall in the same /64 network, or prefix-length must be greater than or equal to 64 except that shorter prefix lengths than 64 are allowed only if non-sequential names are in use.
.TP .TP
.B --dumpfile=<path/to/file> .B --dumpfile=<path/to/file>
Specify the location of a pcap-format file which dnsmasq uses to dump copies of network packets for debugging purposes. If the file exists when dnsmasq starts, it is not deleted; new packets are added to the end. Specify the location of a pcap-format file which dnsmasq uses to dump copies of network packets for debugging purposes. If the file exists when dnsmasq starts, it is not deleted; new packets are added to the end. The file may be a named-pipe which Wireshark is listening to.
.TP .TP
.B --dumpmask=<mask> .B --dumpmask=<mask>
Specify which types of packets should be added to the dumpfile. The argument should be the OR of the bitmasks for each type of packet to be dumped: it can be specified in hex by preceding the number with 0x in the normal way. Each time a packet is written to the dumpfile, dnsmasq logs the packet sequence and the mask Specify which types of packets should be added to the dumpfile. The argument should be the OR of the bitmasks for each type of packet to be dumped: it can be specified in hex by preceding the number with 0x in the normal way. Each time a packet is written to the dumpfile, dnsmasq logs the packet sequence and the mask

14
src/dump.c
View File

@@ -51,9 +51,6 @@ void dump_init(void)
packet_count = 0; packet_count = 0;
if (stat(daemon->dump_file, &buf) == -1)
{
/* doesn't exist, create and add header */
header.magic_number = 0xa1b2c3d4; header.magic_number = 0xa1b2c3d4;
header.version_major = 2; header.version_major = 2;
header.version_minor = 4; header.version_minor = 4;
@@ -62,11 +59,22 @@ void dump_init(void)
header.snaplen = daemon->edns_pktsz + 200; /* slop for IP/UDP headers */ header.snaplen = daemon->edns_pktsz + 200; /* slop for IP/UDP headers */
header.network = 101; /* DLT_RAW http://www.tcpdump.org/linktypes.html */ header.network = 101; /* DLT_RAW http://www.tcpdump.org/linktypes.html */
if (stat(daemon->dump_file, &buf) == -1)
{
/* doesn't exist, create and add header */
if (errno != ENOENT || if (errno != ENOENT ||
(daemon->dumpfd = creat(daemon->dump_file, S_IRUSR | S_IWUSR)) == -1 || (daemon->dumpfd = creat(daemon->dump_file, S_IRUSR | S_IWUSR)) == -1 ||
!read_write(daemon->dumpfd, (void *)&header, sizeof(header), RW_WRITE)) !read_write(daemon->dumpfd, (void *)&header, sizeof(header), RW_WRITE))
die(_("cannot create %s: %s"), daemon->dump_file, EC_FILE); die(_("cannot create %s: %s"), daemon->dump_file, EC_FILE);
} }
else if (S_ISFIFO(buf.st_mode))
{
/* File is named pipe (with wireshark on the other end, probably.)
Send header. */
if ((daemon->dumpfd = open(daemon->dump_file, O_APPEND | O_RDWR)) == -1 ||
!read_write(daemon->dumpfd, (void *)&header, sizeof(header), RW_WRITE))
die(_("cannot open pipe %s: %s"), daemon->dump_file, EC_FILE);
}
else if ((daemon->dumpfd = open(daemon->dump_file, O_APPEND | O_RDWR)) == -1 || else if ((daemon->dumpfd = open(daemon->dump_file, O_APPEND | O_RDWR)) == -1 ||
!read_write(daemon->dumpfd, (void *)&header, sizeof(header), RW_READ)) !read_write(daemon->dumpfd, (void *)&header, sizeof(header), RW_READ))
die(_("cannot access %s: %s"), daemon->dump_file, EC_FILE); die(_("cannot access %s: %s"), daemon->dump_file, EC_FILE);