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wpa/hostapd: Fix 100% CPU when USB wlan NIC removed

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hostapd calls pcap_next(3) to read the next packet off the wlan interface.
pcap_next() returns a pointer to the packet header but does not indicate
success or failure. Unfortunately this results in an infinite loop (100%
CPU) when the wlan device disappears, i.e. when a USB wlan device is
manually removed or a USB error results in the device removal. However
pcap_next_ex(3) does return success or failure. To resolve this we use
pcap_next_ex(), forcing hostapd to exit when the error is encountered.

An error message is printed to syslog or stderr when debugging (-d flag)
is enabled. Unfortunately wpa_printf() only works when debugging is enabled.

PR:		253608
Reported by:	Damjan Jovanovic <damjan.jov@gmail.com>,
		bz (privately)
MFC after:	3 days
This commit is contained in:
Cy Schubert 2022-04-02 20:54:50 -07:00
parent db2d56ca01
commit 6e5d01124f
1 changed files with 4 additions and 1 deletions
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5
contrib/wpa/src/l2_packet/l2_packet_freebsd.c
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@ -83,7 +83,10 @@ static void l2_packet_receive(int sock, void *eloop_ctx, void *sock_ctx)
unsigned char *buf;
size_t len;
packet = pcap_next(pcap, &hdr);
if (pcap_next_ex(pcap, &hdr, &packet) == -1) {
wpa_printf(MSG_ERROR, "Error reading packet, has device disappeared?");
eloop_terminate();
}
if (!l2->rx_callback || !packet || hdr.caplen < sizeof(*ethhdr))
return;