PCAP_INJECT(3PCAP) PCAP_INJECT(3PCAP)

NAME

pcap_inject, pcap_sendpacket - transmit a packet

SYNOPSIS

#include <pcap/pcap.h>

int pcap_inject(pcap_t *p, const void *buf, size_t size);
int pcap_sendpacket(pcap_t *p, const u_char *buf, int size);

DESCRIPTION

pcap_inject() sends a raw packet through the network interface; buf
points to the data of the packet, including the link-layer header,
and size is the number of bytes in the packet.

Note that, even if you successfully open the network interface, you
might not have permission to send packets on it, or it might not
support sending packets; as pcap_open_live(3PCAP) doesn't have a flag
to indicate whether to open for capturing, sending, or capturing and
sending, you cannot request an open that supports sending and be
notified at open time whether sending will be possible. Note also
that some devices might not support sending packets.

Note that, on some platforms, the link-layer header of the packet
that's sent might not be the same as the link-layer header of the
packet supplied to pcap_inject(), as the source link-layer address,
if the header contains such an address, might be changed to be the
address assigned to the interface on which the packet it sent, if the
platform doesn't support sending completely raw and unchanged
packets. Even worse, some drivers on some platforms might change the
link-layer type field to whatever value libpcap used when attaching
to the device, even on platforms that do nominally support sending
completely raw and unchanged packets.

pcap_sendpacket() is like pcap_inject(), but it returns 0 on success,
rather than returning the number of bytes written. (pcap_inject()
comes from OpenBSD; pcap_sendpacket() comes from WinPcap/Npcap. Both
are provided for compatibility.)

RETURN VALUE

pcap_inject() returns the number of bytes written on success,
PCAP_ERROR_NOT_ACTIVATED if called on a capture handle that has been
created but not activated, and PCAP_ERROR on other errors.

pcap_sendpacket() returns 0 on success, PCAP_ERROR_NOT_ACTIVATED if
called on a capture handle that has been created but not activated,
and PCAP_ERROR on other errors.

If PCAP_ERROR is returned, pcap_geterr(3PCAP) or pcap_perror(3PCAP)
may be called with p as an argument to fetch or display the error
text.

SEE ALSO

pcap(3PCAP)

5 March 2022 PCAP_INJECT(3PCAP)