NG_CHECKSUM(4)         FreeBSD Kernel Interfaces Manual         NG_CHECKSUM(4)

NAME
     ng_checksum - reconstructing IP checksums node type

SYNOPSIS
     #include <netgraph/ng_checksum.h>

DESCRIPTION
     The checksum node can calculate, or prepare for calculation in hardware,
     IPv4 header, TCP and UDP checksums.

HOOKS
     This node type has two hooks:

     in       Packets received on this hook are processed according to
              settings specified in config and then forwarded to the out hook,
              if it exists and is connected.  Otherwise they are reflected
              back to the in hook.

     out      Packets received on this hook are forwarded to the in hook
              without any changes.

CONTROL MESSAGES
     This node type supports the generic control messages, plus the following:

     NGM_CHECKSUM_SETDLT (setdlt)
          Sets the data link type on the in hook.  Currently, supported types
          are DLT_RAW (raw IP datagrams) and DLT_EN10MB (Ethernet). DLT_
          definitions can be found in the <net/bpf.h> header.  Currently used
          values are DLT_EN10MB = 1 and DLT_RAW = 12.

     NGM_CHECKSUM_GETDLT (getdlt)
          This control message obtains the data link type on the in hook.

     NGM_CHECKSUM_SETCONFIG (setconfig)
          Sets the node configuration.  The following struct
          ng_checksum_config must be supplied as an argument:

              struct ng_checksum_config {
                      uint64_t        csum_flags;
                      uint64_t        csum_offload;
              };

          The csum_flags can be set to any combination of CSUM_IP, CSUM_TCP,
          CSUM_UDP, CSUM_TCP_IPV6 and CSUM_UDP_IPV6 (other values are ignored)
          for instructing the node to calculate the corresponding checksum.

          The csum_offload value can be set to any combination of CSUM_IP,
          CSUM_TCP, CSUM_UDP, CSUM_TCP_IPV6 and CSUM_UDP_IPV6 (other values
          are ignored) for instructing the node what checksums should be
          requested from the hardware.

          The node also takes into account any combination of CSUM_IP,
          CSUM_TCP, CSUM_UDP, CSUM_TCP_IPV6 and CSUM_UDP_IPV6 already flagged
          on the mbuf.

     NGM_CHECKSUM_GETCONFIG (getconfig)
          This control message obtains the current node configuration returned
          as a struct ng_checksum_config.

     NGM_CHECKSUM_GET_STATS (getstats)
          Returns node statistics as a struct ng_checksum_stats.

     NGM_CHECKSUM_CLR_STATS (clrstats)
          Clear the node statistics.

     NGM_CHECKSUM_GETCLR_STATS (getclrstats)
          This command is identical to NGM_CHECKSUM_GET_STATS, except that the
          statistics are also atomically cleared.

SHUTDOWN
     This node shuts down upon receipt of a NGM_SHUTDOWN control message, or
     when all hooks have been disconnected.

EXAMPLES
     ngctl(8) script:

         /usr/sbin/ngctl -f- <<-SEQ
                 msg checksum-1: setdlt 1
                 msg checksum-1: setconfig { csum_flags=0 csum_offload=6 }
         SEQ

     Set the data link type to DLT_EN10MB (Ethernet), do not set additional
     checksum flags and request that the hardware calculate
     CSUM_IP_UDP|CSUM_IP_TCP.

SEE ALSO
     netgraph(4), ng_patch(4), ngctl(8)

HISTORY
     The ng_checksum node type was implemented in FreeBSD 10.2 and first
     submitted in FreeBSD 12.0.

AUTHORS
     Dmitry Vagin <daemon.hammer@ya.ru>.

FreeBSD 13.1-RELEASE-p6        October 29, 2015        FreeBSD 13.1-RELEASE-p6