.\" Copyright (c) 2020 Ryan Moeller <freqlabs@FreeBSD.org>
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.Dd December 6, 2023
.Dt CAP_NETDB 3
.Os
.Sh NAME
.Nm cap_getprotobyname ,
.Nd "library for getting network proto entry in capability mode"
.Sh LIBRARY
.Lb libcap_netdb
.Sh SYNOPSIS
.In sys/nv.h
.In libcasper.h
.In casper/cap_netdb.h
.Ft "struct protoent *"
.Fn cap_getprotobyname "const cap_channel_t *chan" "const char *name"
.Sh DESCRIPTION
The function
.Fn cap_getprotobyname
is equivalent to
.Xr getprotobyname 3
except that the connection to the
.Nm system.netdb
service needs to be provided.
It is reentrant but not thread-safe.
That is, it may be called from separate threads only with different
.Vt cap_channel_t
arguments or with synchronization.
.Sh EXAMPLES
The following example first opens a capability to casper and then uses this
capability to create the
.Nm system.netdb
casper service and uses it to look up a protocol by name.
.Bd -literal
cap_channel_t *capcas, *capnetdb;
struct protoent *ent;

/* Open capability to Casper. */
capcas = cap_init();
if (capcas == NULL)
	err(1, "Unable to contact Casper");

/* Enter capability mode sandbox. */
if (caph_enter() < 0)
	err(1, "Unable to enter capability mode");

/* Use Casper capability to create capability to the system.netdb service. */
capnetdb = cap_service_open(capcas, "system.netdb");
if (capnetdb == NULL)
	err(1, "Unable to open system.netdb service");

/* Close Casper capability, we don't need it anymore. */
cap_close(capcas);

ent = cap_getprotobyname(capnetdb, "http");
if (ent == NULL)
       errx(1, "cap_getprotobyname failed to find http proto");
.Ed
.Sh SEE ALSO
.Xr cap_enter 2 ,
.Xr caph_enter 3 ,
.Xr err 3 ,
.Xr getprotobyname 3 ,
.Xr capsicum 4 ,
.Xr nv 9
.Sh AUTHORS
The
.Nm cap_netdb
service was implemented by
.An Ryan Moeller Aq Mt freqlabs@FreeBSD.org .