Debarshi Ray wrote: > > What's the use-case of this function? You said that you want to "safely" > > read from sockfd, but can you explain what you mean by that? > > I am actually reading from a PF_NETLINK socket and want the entire > data, which can be spread over multiple consecutive messages, in a > buffer.
I see... > Now the BUFSIZ documentation says its "value is guaranteed to > be at least `256'". It is at least 512 everywhere in practice: 512 on mingw 1024 on MacOS X, FreeBSD, OpenBSD, NetBSD, HP-UX, Solaris, Interix, QNX, Cygwin 4096 on AIX, IRIX 8192 on glibc, OSF/1 > Using read-file might not always be possbile since we would lose the > 'flags' argument of 'recv'. But so far your function uses a flags argument of 0. Would any of the flag values MSG_OOB, MSG_PEEK, MSG_WAITALL make sense here? > there are instances where having the entire data in a buffer > makes it easier to parse it. eg., the routing table example. Sure. But your function does not produce the entire data: it does not read until EOF. It reads only as far as is available. When more packets become available, they will be returned through another recvbuf invocation, thus they will have to be parsed separately. In particular, the parser cannot assume that it has the entire data, otherwise it has timing related bugs. This holds for TCP sockets. NETLINK sockets may well be different; I have no experience with them. Bruno
