allow specifying gsmtap dest ip

This allows distinguishing multiple modems by specifying another
loopback ip i.e. -i 127.0.0.4
Linux has a default local route for 127.0.0.0/8 so it "just works".
hoernchen/gsmtap
Eric Wild 2020-12-09 04:24:13 +01:00
parent 4846c50521
commit acb80088b3
3 changed files with 48 additions and 5 deletions

5
README
View File

@ -16,6 +16,11 @@ This requires tcpdump, as well as the required permissions
to capture, i.e. on ubuntu this can be conveniently achieved by
sudo setcap cap_net_raw,cap_net_admin=ep /usr/sbin/tcpdump
In order to distinguish multiple different modems in the capture file
passing a GSMTAP destination ip is possible with the -i parameter, i.e.
./capture.sh -s /dev/ttyUSB0 -f outfilename.pcap -i 127.0.0.4
This will "just work" on linux, since there is a default 127.0.0.0/8 route.
Additionally wireshark needs Edit->Preferences->Protocols->NAS-EPS
"Force dissect as plain EPS" set to true, since capturing encrypted NAS
messages is fairly useless (although possible), so unencrypted

View File

@ -3,6 +3,7 @@
while [[ "$#" -gt 0 ]]; do
case $1 in
-s|--serialpath) serialpath="$2"; shift ;;
-i|--ip) gsmtapip="$2"; shift ;;
-f|--filename) filename="$2"; shift ;;
-Q|--qcdebug) qcdebug=1 ;;
*) echo "unknown parameter: $1"; exit 1 ;;
@ -10,8 +11,16 @@ while [[ "$#" -gt 0 ]]; do
shift
done
killall tcpdump
#killall tcpdump
if [ -n "$gsmtapip" ]; then
tcpdump -i any udp port 4729 and dst $gsmtapip -w $filename &
tcpdump_pid=$!
./src/osmo-qcdiag-log -s $serialpath -G -i $gsmtapip
else
tcpdump -i any udp port 4729 -w $filename &
tcpdump_pid=$!
./src/osmo-qcdiag-log -s $serialpath -G
fi
kill -9 $tcpdump_pid

View File

@ -38,6 +38,7 @@
#include <osmocom/core/serial.h>
#include <osmocom/core/gsmtap_util.h>
#include <osmocom/core/gsmtap.h>
#include <osmocom/core/socket.h>
#include <osmocom/core/logging.h>
#include "diag_io.h"
@ -52,6 +53,7 @@
struct diag_instance di;
static char *serial_path = 0;
static uint32_t cfg_flags = 0;
static char *gsmtap_ip = "localhost";
static void do_configure(struct diag_instance *di)
{
@ -184,6 +186,7 @@ static void print_help()
" -G --gsmtap GSMTAP messages sent to localhost\n"
" -Q --qcomdbg plain QC DIAG GSMTAP messages\n"
" -H --hexdump console output of rx/tx messages\n"
" -i --ip address the GSMTAP packets should be sent to (default 127.0.0.1)\n"
);
}
@ -197,10 +200,11 @@ static void handle_options(int argc, char **argv)
{ "qcomdbg", 0, 0, 'Q' },
{ "hexdump", 0, 0, 'H' },
{ "serial-path", 1, 0, 's' },
{ "ip", 1, 0, 'i' },
{ 0, 0, 0, 0 }
};
c = getopt_long(argc, argv, "hGQHs:", long_options, &option_index);
c = getopt_long(argc, argv, "hGQHs:i:", long_options, &option_index);
if (c == -1)
break;
@ -220,10 +224,36 @@ static void handle_options(int argc, char **argv)
case 's':
serial_path = optarg;
break;
case 'i':
gsmtap_ip = optarg;
break;
}
}
}
/* special function that allows to bind to local nonlocal ips like 127.0.0.x with x != 1 */
static int gsmtap_source_add_local_sink(struct gsmtap_inst *gti)
{
int rc;
struct sockaddr_storage ss;
socklen_t ss_len = sizeof(ss);
if (gti->ofd_wq_mode)
return -1;
rc = getpeername(gsmtap_inst_fd(gti), (struct sockaddr *)&ss, &ss_len);
if (rc < 0)
return rc;
rc = osmo_sock_init_sa((struct sockaddr *)&ss, SOCK_DGRAM,
IPPROTO_UDP,
OSMO_SOCK_F_BIND |
OSMO_SOCK_F_UDP_REUSEADDR);
if (rc >= 0)
return rc;
return -ENODEV;
}
int main(int argc, char **argv)
{
@ -258,15 +288,14 @@ int main(int argc, char **argv)
tio.c_cc[VTIME] = 0;
rc = tcsetattr(di.fd, TCSANOW, &tio);
di.gsmtap = gsmtap_source_init("localhost", GSMTAP_UDP_PORT, 0);
di.gsmtap = gsmtap_source_init(gsmtap_ip, GSMTAP_UDP_PORT, 0);
if (di.gsmtap == 0) {
printf("error initializing gsmtap source!\n");
return EXIT_FAILURE;
}
di.flags = cfg_flags;
rc = gsmtap_source_add_sink(di.gsmtap);
rc = gsmtap_source_add_local_sink(di.gsmtap);
if (rc < 0) {
printf("error initializing gsmtap sink!\n");
return EXIT_FAILURE;