Hello, any objections against the patch? On Thu, 2017-10-26 at 15:06 +0200, Nikola Forró wrote: > When an underlying recvmsg call fails after at least one message has > been received, recvmmsg stores the error code into sock->sk->sk_err, > and returns it on a subsequent call. But it doesn't take into account > that the error can be owerwritten in the meantime, for example in ICMP > error handler when an ICMP packet arrives. > > When an underlying sendmsg call fails after at least one message has > been sent, sendmmsg discards the error code and expects the caller to > retry at first failed message. But the error code returned from the > subsqeuent call can be different from the previously discarded one. > > Reference: > https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git/tree/net/socket.c > > Signed-off-by: Nikola Forró <nforro@xxxxxxxxxx> > --- > man2/recvmmsg.2 | 12 ++++++++++++ > man2/sendmmsg.2 | 8 ++++++++ > 2 files changed, 20 insertions(+) > > diff --git a/man2/recvmmsg.2 b/man2/recvmmsg.2 > index 3ff1b63a3..ca05b1d3a 100644 > --- a/man2/recvmmsg.2 > +++ b/man2/recvmmsg.2 > @@ -160,6 +160,8 @@ In addition, the following error can occur: > .B EINVAL > .I timeout > is invalid. > +.PP > +See also BUGS. > .SH VERSIONS > The > .BR recvmmsg () > @@ -179,6 +181,16 @@ so that if up to > .I vlen\-1 > datagrams are received before the timeout expires, > but then no further datagrams are received, the call will block forever. > +.PP > +If an error occurs on an underlying > +.BR recvmsg (2) > +call after at least one message has been received, the call succeeds, > +and returns the number of messages received. The error code is expected > +to be returned on a subsequent call to > +.BR recvmmsq (). > +However, in the current implementation the error code can be overwritten > +in the meantime by an unrelated network event on a socket, > +for example an incoming ICMP packet. > .SH EXAMPLE > .PP > The following program uses > diff --git a/man2/sendmmsg.2 b/man2/sendmmsg.2 > index e61ed0b4e..2f4bbeb01 100644 > --- a/man2/sendmmsg.2 > +++ b/man2/sendmmsg.2 > @@ -134,6 +134,7 @@ is set to indicate the error. > Errors are as for > .BR sendmsg (2). > An error is returned only if no datagrams could be sent. > +See also BUGS. > .\" commit 728ffb86f10873aaf4abd26dde691ee40ae731fe > .\" ... only return an error if no datagrams could be sent. > .\" If less than the requested number of messages were sent, the application > @@ -165,6 +166,13 @@ is capped to > .\" For error handling an application using sendmmsg needs to retry at > .\" the first unsent message, so capping is simpler and requires less > .\" application logic than returning EINVAL. > +.SH BUGS > +If an error occurs on an underlying > +.BR sendmsg (2) > +call after at least one message has been sent, the call succeeds, > +and returns the number of messages sent. The error code is lost. > +The caller can retry starting at first failed message, but there is > +no guarantee that the error returned will be the same as the previous one. > .SH EXAMPLE > The example below uses > .BR sendmmsg () -- To unsubscribe from this list: send the line "unsubscribe linux-man" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
