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Disable TPACKET v3 to prevent packets reordering in root mode

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It seems like TPACKET V3 causes packet reordering issues, where a packet
A sent before a packet B by the same host is actually seen after B in
the capture. This causes inexistent out-of-order and missing TCP segments
issues in Wireshark.

This has been verified by comparing the PCAP dump generated by PCAPdroid
in HTTP server mode with the traffic dump on the LAN, thus excluding
reordering occuring over the Internet.
This commit is contained in:
emanuele-f 2022-01-26 15:50:44 +01:00
parent 5e9be5cd8b
commit f715c06be1
1 changed files with 13 additions and 1 deletions
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14
app/src/main/jni/pcapd/pcapd.c
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@ -417,7 +417,19 @@ static int open_interface(pcapd_iface_t *iface, pcapd_runtime_t *rt, const char
/* The snaplen includes the datalink overhead. Max datalink overhead (SLL2): 20 B */
int snaplen = mtu + SLL2_HDR_LEN;
pcap_t *pd = pcap_open_live(ifname, snaplen, 0, 1, errbuf);
// pcap_set_immediate_mode necessary to avoid using TPACKET v3, which sometimes causes packets
// reordering in the capture
pcap_t *pd;
if(!(pd = pcap_create(ifname, errbuf)) ||
pcap_set_immediate_mode(pd, 1) ||
pcap_set_snaplen(pd, snaplen) ||
pcap_activate(pd)) {
if(pd) {
pcap_close(pd);
pd = NULL;
}
}
if(!pd) {
// try to open as file
pd = pcap_open_offline(ifname, errbuf);