[Bug] Reachable assertion in packet2tree()

[Marsman1996]

Describe the bug
The assertion assert(l2len > 0); in packet2tree() at tree.c is reachable when the user uses tcpprep to open a crafted pcap file.
The variable l2len is assigned in get_l2len_protocol() at get.c.

tcpreplay/src/tree.c

Lines 733 to 746 in 09f0774

	res = get_l2len_protocol(data,
	pkt_len,
	datalink,
	&ether_type,
	&l2len,
	&l2offset,
	&vlan_offset);
	if (res == -1)
	goto len_error;
	node = new_tree();
	assert(l2len > 0);

However, when the datalink is DLT_RAW or DLT_JUNIPER_ETHER, l2len is assigned with 0, and the assertion is triggered.

tcpreplay/src/common/get.c

Lines 268 to 282 in 09f0774

	*l2len = 0;
	*l2offset = 0;
	*vlan_offset = 0;
	switch (datalink) {
	case DLT_RAW:
	if (datalen == 0)
	return -1;
	if ((pktdata[0] >> 4) == 4)
	*protocol = ETHERTYPE_IP;
	else if ((pktdata[0] >> 4) == 6)
	*protocol = ETHERTYPE_IP6;
	break;
	case DLT_JUNIPER_ETHER:

To Reproduce
Steps to reproduce the behavior:

1. Get the Tcpreplay source code (master 09f0774) and compile it.
2. Run command: $ tcpprep --auto=bridge --pcap=$POC --cachefile=/dev/null
   The POC file could be downloaded here:
   POC_file

Expected behavior
Program reports assertion failure and is terminated.

Screenshots

The GDB report:

Breakpoint 6, packet2tree (data=0x7ffff7ef8010 "@", len=33, datalink=12) at ../../code/src/tree.c:733
733         res = get_l2len_protocol(data,
(gdb) p datalink 
$8 = 12
(gdb) n
741         if (res == -1)
(gdb) 
744         node = new_tree();
(gdb) 

Breakpoint 1, packet2tree (data=0x7ffff7ef8010 "@", len=33, datalink=<optimized out>) at ../../code/src/tree.c:746
746         assert(l2len > 0);
(gdb) p l2len 
$9 = 0
(gdb) c
Continuing.
tcpprep: ../../code/src/tree.c:746: tcpr_tree_t *packet2tree(const u_char *, const int, int): Assertion `l2len > 0' failed.

Program received signal SIGABRT, Aborted.
0x00007ffff7194438 in __GI_raise (sig=sig@entry=6) at ../sysdeps/unix/sysv/linux/raise.c:54
54      ../sysdeps/unix/sysv/linux/raise.c: No such file or directory.

System (please complete the following information):

• OS: Ubuntu
• OS version: 16.04, 64 bit
• Tcpreplay Version: 4.4.1 (master 09f0774)

[fklassen]

Unable to recreate. What is your ./configure command?

Here is my log:

$ ./configure --with-testnic=ens33
...
$ make
...
$ src/tcpprep --auto=bridge --pcap=$POC --cachefile=/dev/null

Fatal Error: Error opening file: invalid file capture length 264194, bigger than maximum of 262144

[fklassen]

Closing as "Cannot reproduce" however I believe that whatever you are seeing may be fixed with #716.

[fklassen]

Able to reproduce with #746 and to be fixed in 4.4.3. #678, commit 46cf964a