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osmo-pcap
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client: Set snaplen to MAXIMUM_SNAPLEN 

Despite this value not being exported publicly, the truth is that
tcpdump and wireshark nowadays avoid processing any file with snaplen
bigger than this value:
"tcpdump: pcap_loop: invalid packet capture length 861244, bigger than
snaplen of 262144"
It also fails to set snaplen to values bigger than that:
"tcpdump -s 262145" --> "tcpdump: invalid snaplen 262145"

pcapfix also warns about wrong packet length if bigger than same value
(defined as PCAP_MAX_SNAPLEN there).

MAXIMUM_SPANPLEN is defined in tcpdump's netdissect.h and libpcap's
pcap-int.h. It is also defined as WTAP_MAX_PACKET_SIZE in
wireshark/wiretap/wtap.h (this one being the only publicly available).

Change-Id: Ib7449d5aba9da342c150704ebd0e1f09e7f7276c
This commit is contained in:
Pau Espin 2018-10-08 11:41:33 +02:00
parent db7be44632
commit 168949e119
2 changed files with 6 additions and 2 deletions
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5
include/osmo-pcap/common.h
View File

@ -58,4 +58,9 @@ extern const char *osmopcap_copyright;
extern int osmopcap_go_parent(struct vty *vty);
extern int osmopcap_is_config_node(struct vty *vty, int node);
/* defined in libpcap's pcap-int.h, which is not public */
#ifndef MAXIMUM_SNAPLEN
#define MAXIMUM_SNAPLEN 262144
#endif
#endif

3
src/osmo_client_network.c
View File

@ -42,7 +42,6 @@
#include <string.h>
#include <unistd.h>
static void _osmo_client_connect(void *_data)
{
osmo_client_connect((struct osmo_pcap_client_conn *) _data);
@ -257,7 +256,7 @@ void osmo_client_send_link(struct osmo_pcap_client_conn *conn)
hdr->version_minor = 4;
hdr->thiszone = 0;
hdr->sigfigs = 0;
hdr->snaplen = UINT_MAX;
hdr->snaplen = MAXIMUM_SNAPLEN;
hdr->linktype = pcap_datalink(conn->client->handle);
write_data(conn, msg);