__SKB_TRY_RECV_DATAG(9)                  Linux Networking                 __SKB_TRY_RECV_DATAG(9)



NAME
       __skb_try_recv_datagram - Receive a datagram skbuff

SYNOPSIS
       struct sk_buff * __skb_try_recv_datagram(struct sock * sk, unsigned int flags,
                                                int * peeked, int * off, int * err,
                                                struct sk_buff ** last);

ARGUMENTS
       sk
           socket

       flags
           MSG_ flags

       peeked
           returns non-zero if this packet has been seen before

       off
           an offset in bytes to peek skb from. Returns an offset within an skb where data
           actually starts

       err
           error code returned

       last
           set to last peeked message to inform the wait function what to look for when peeking

DESCRIPTION
       Get a datagram skbuff, understands the peeking, nonblocking wakeups and possible races.
       This replaces identical code in packet, raw and udp, as well as the IPX AX.25 and
       Appletalk. It also finally fixes the long standing peek and read race for datagram
       sockets. If you alter this routine remember it must be re-entrant.

       This function will lock the socket if a skb is returned, so the caller needs to unlock the
       socket in that case (usually by calling skb_free_datagram). Returns NULL with *err set to
       -EAGAIN if no data was available or to some other value if an error was detected.

       * It does not lock socket since today. This function is * free of race conditions. This
       measure should/can improve * significantly datagram socket latencies at high loads, * when
       data copying to user space takes lots of time. * (BTW I've just killed the last cli in
       IP/IPv6/core/netlink/packet * 8) Great win.) * --ANK (980729)

       The order of the tests when we find no data waiting are specified quite explicitly by
       POSIX 1003.1g, don't change them without having the standard around please.

COPYRIGHT
Kernel Hackers Manual 4.8.                 January 2017                   __SKB_TRY_RECV_DATAG(9)