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  20 .TH PCAP_INJECT 3PCAP "23 November 2024"
  21 .SH NAME
  22 pcap_inject, pcap_sendpacket \- transmit a packet
  23 .SH SYNOPSIS
  24 .nf
  25 .ft B
  26 #include <pcap/pcap.h>
  27 .ft
  28 .LP
  29 .ft B
  30 int pcap_inject(pcap_t *p, const void *buf, size_t size);
  31 int pcap_sendpacket(pcap_t *p, const u_char *buf, int size);
  32 .ft
  33 .fi
  34 .SH DESCRIPTION
  35 .BR pcap_inject ()
  36 sends a raw packet through the network interface;
  37 .I buf
  38 points to the data of the packet, including the link-layer header, and
  39 .I size
  40 is the number of bytes in the packet.
  41 .PP
  42 Note that, even if you successfully open the network interface, you
  43 might not have permission to send packets on it, or it might not support
  44 sending packets; as
  45 .BR pcap_open_live (3PCAP)
  46 doesn't have a flag to indicate whether to open for capturing, sending,
  47 or capturing and sending, you cannot request an open that supports
  48 sending and be notified at open time whether sending will be possible.
  49 The same limitation applies to
  50 .BR \%pcap_create (3PCAP)
  51 and
  52 .BR \%pcap_activate (3PCAP).
  53 Note also that some devices might not support sending packets.
  54 .PP
  55 Note that, on some platforms, the link-layer header of the packet that's
  56 sent might not be the same as the link-layer header of the packet
  57 supplied to
  58 .BR pcap_inject (),
  59 as the source link-layer address, if the header contains such an
  60 address, might be changed to be the address assigned to the interface on
  61 which the packet it sent, if the platform doesn't support sending
  62 completely raw and unchanged packets.  Even worse, some drivers on some
  63 platforms might change the link-layer type field to whatever value
  64 libpcap used when attaching to the device, even on platforms that
  65 .I do
  66 nominally support sending completely raw and unchanged packets.
  67 .PP
  68 .BR pcap_sendpacket ()
  69 is like
  70 .BR pcap_inject (),
  71 but it returns
  72 .B 0
  73 on success, rather than returning the number of bytes
  74 written.
  75 .RB ( pcap_inject ()
  76 comes from OpenBSD;
  77 .BR pcap_sendpacket ()
  78 comes from WinPcap/Npcap.  Both are provided for compatibility.)
  79 .SH RETURN VALUE
  80 .BR pcap_inject ()
  81 returns the number of bytes written on success,
  82 .B PCAP_ERROR_NOT_ACTIVATED
  83 if called on a capture handle that has been created but not activated, and
  84 .B PCAP_ERROR
  85 on other errors.
  86 .PP
  87 .BR pcap_sendpacket ()
  88 returns
  89 .B 0
  90 on success,
  91 .B PCAP_ERROR_NOT_ACTIVATED
  92 if called on a capture handle that has been created but not activated, and
  93 .B PCAP_ERROR
  94 on other errors.
  95 .PP
  96 If
  97 .B PCAP_ERROR
  98 is returned,
  99 .BR pcap_geterr (3PCAP)
 100 or
 101 .BR pcap_perror (3PCAP)
 102 may be called with
 103 .I p
 104 as an argument to fetch or display the error text.
 105 .SH SEE ALSO
 106 .BR pcap (3PCAP)