recv.2 (2010 09)

r
recv(2) recv(2)
• The MSG_OOB flag is supported.
• The
MSG_PEEK flag is supported; the two flags can be combined.
• If a message is received that is larger than the user-controlled maximum message size, the X.25 sub-
system RESETs the circuit, discards the data, and sends the out-of-band event
OOB_VC_MESSAGE_TOO_BIG
to the socket.
X/Open Sockets Only
For
X/Open Sockets, the msghdr
structure has the following form:
(UNIX 03)
struct msghdr {
void *msg_name; /* optional address */
socklen_t msg_namelen; /* size of address */
struct iovec *msg_iov; /* scatter array for data */
int msg_iovlen; /* # of elements in msg_iov */
void *msg_control; /* ancillary data, see below */
socklen_t msg_controllen; /* ancillary data buffer len */
int msg_flags; /* flags on received message */
}
Obsolescent (UNIX 95)
struct msghdr {
void *msg_name; /* optional address */
size_t msg_namelen; /* size of address */
struct iovec *msg_iov; /* scatter array for data */
int msg_iovlen; /* # of elements in msg_iov */
void *msg_control; /* ancillary data, see below */
size_t msg_controllen; /* ancillary data buffer len */
int msg_flags; /* flags on received message */
}
msg_control specifies a buffer to receive any ancillary data sent along with the message. Ancillary data
consists of a sequence of pairs, each consisting of a cmsghdr structure followed by a data array. The
data array contains the ancillary data message, and the cmsghdr structure contains descriptive informa-
tion that allows an application to correctly parse the data. cmsghdr has the following structure:
(UNIX 03)
struct cmsghdr {
socklen_t cmsg_len; /* data byte count, including hdr*/
int cmsg_level; /* originating protocol */
int cmsg_type; /* protocol-specific type */
}
Obsolescent (UNIX 95)
struct cmsghdr {
size_t cmsg_len; /* data byte count, including hdr*/
int cmsg_level; /* originating protocol */
int cmsg_type; /* protocol-specific type */
}
If the cmsg_level is SOL_SOCKET, and cmsg_type is SCM_RIGHTS, then it indicates that the data array
contains the access rights to be received. Access rights are supported only for AF_UNIX. Access rights
are limited to file descriptors of size int .
If the cmsg_level is
IPPROTO_IPV6, then cmsg_type must be one of the supported types:
IPV6_PKTINFO, IPV6_HOPLIMIT, IPV6_NEXTHOP, IPV6_RTHDR, IPV6_HOPOPTS,
IPV6_DSTOPTS or IPV6_RTHDRDSTOPTS. (See description in IPv6(7P)).
If ancillary data are not being transferred, set the msg_control field to NULL, and set the msg_controllen
field to 0.
4 Hewlett-Packard Company − 4 − HP-UX 11i Version 3: September 2010