From 95430c0b140c31cb9e39f876afe1c0e9947d1aaf Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?R=C3=A9mi=20Denis-Courmont?= Date: Sun, 5 Oct 2008 11:16:36 -0700 Subject: Phonet: pipe end-point protocol documentation MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Signed-off-by: Rémi Denis-Courmont Signed-off-by: David S. Miller --- Documentation/networking/phonet.txt | 54 +++++++++++++++++++++++++++++++++++++ 1 file changed, 54 insertions(+) (limited to 'Documentation/networking') diff --git a/Documentation/networking/phonet.txt b/Documentation/networking/phonet.txt index 57d3e59edb1..0e6e592f4f5 100644 --- a/Documentation/networking/phonet.txt +++ b/Documentation/networking/phonet.txt @@ -112,6 +112,60 @@ However, connect() and getpeername() are not supported, as they did not seem useful with Phonet usages (could be added easily). +Phonet Pipe protocol +-------------------- + +The Phonet Pipe protocol is a simple sequenced packets protocol +with end-to-end congestion control. It uses the passive listening +socket paradigm. The listening socket is bound to an unique free object +ID. Each listening socket can handle up to 255 simultaneous +connections, one per accept()'d socket. + + int lfd, cfd; + + lfd = socket(PF_PHONET, SOCK_SEQPACKET, PN_PROTO_PIPE); + listen (lfd, INT_MAX); + + /* ... */ + cfd = accept(lfd, NULL, NULL); + for (;;) + { + char buf[...]; + ssize_t len = read(cfd, buf, sizeof(buf)); + + /* ... */ + + write(cfd, msg, msglen); + } + +Connections are established between two endpoints by a "third party" +application. This means that both endpoints are passive; so connect() +is not possible. + +WARNING: +When polling a connected pipe socket for writability, there is an +intrinsic race condition whereby writability might be lost between the +polling and the writing system calls. In this case, the socket will +block until write because possible again, unless non-blocking mode +becomes enabled. + + +The pipe protocol provides two socket options at the SOL_PNPIPE level: + + PNPIPE_ENCAP accepts one integer value (int) of: + + PNPIPE_ENCAP_NONE: The socket operates normally (default). + + PNPIPE_ENCAP_IP: The socket is used as a backend for a virtual IP + interface. This requires CAP_NET_ADMIN capability. GPRS data + support on Nokia modems can use this. Note that the socket cannot + be reliably poll()'d or read() from while in this mode. + + PNPIPE_IFINDEX is a read-only integer value. It contains the + interface index of the network interface created by PNPIPE_ENCAP, + or zero if encapsulation is off. + + Authors ------- -- cgit v1.2.3