HTML rendering created 2025-09-06 byMichael Kerrisk, author ofThe Linux Programming Interface. For details of in-depthLinux/UNIX system programming training courses that I teach, lookhere. Hosting byjambit GmbH. |  |
NAME |SYNOPSIS |DESCRIPTION |RETURN VALUE |SEE ALSO |COLOPHON | |
PCAP_INJECT(3PCAP)PCAP_INJECT(3PCAP)pcap_inject, pcap_sendpacket - transmit a packet
#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);
pcap_inject() sends a raw packet through the network interface;buf points to the data of the packet, including the link-layer header, andsize 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; aspcap_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. The same limitation applies topcap_create(3PCAP) andpcap_activate(3PCAP). 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 topcap_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 thatdo nominally support sending completely raw and unchanged packets.pcap_sendpacket() is likepcap_inject(), but it returns0on 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.)
pcap_inject() returns the number of bytes written on success,PCAP_ERROR_NOT_ACTIVATEDif called on a capture handle that has been created but not activated, andPCAP_ERRORon other errors.pcap_sendpacket() returns0on success,PCAP_ERROR_NOT_ACTIVATED if called on a capture handle that has been created but not activated, andPCAP_ERRORon other errors. IfPCAP_ERRORis returned,pcap_geterr(3PCAP) orpcap_perror(3PCAP) may be called withp as an argument to fetch or display the error text.
pcap(3PCAP)
This page is part of thelibpcap (packet capture library) project. Information about the project can be found at ⟨http://www.tcpdump.org/⟩. If you have a bug report for this manual page, see ⟨http://www.tcpdump.org/#patches⟩. This page was obtained from the project's upstream Git repository ⟨https://github.com/the-tcpdump-group/libpcap.git⟩ on 2025-08-11. (At that time, the date of the most recent commit that was found in the repository was 2025-08-10.) If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which isnot part of the original manual page), send a mail to man-pages@man7.org 23 November 2024PCAP_INJECT(3PCAP)HTML rendering created 2025-09-06 byMichael Kerrisk, author ofThe Linux Programming Interface. For details of in-depthLinux/UNIX system programming training courses that I teach, lookhere. Hosting byjambit GmbH. | |