2008-08-08 16:41:48 +00:00
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.\" This man page is Copyright (C) 1999 Andi Kleen <ak@muc.de>.
|
ldd.1, capget.2, clone.2, create_module.2, fallocate.2, futex.2, get_kernel_syms.2, get_thread_area.2, getcpu.2, getitimer.2, getpid.2, io_cancel.2, io_destroy.2, io_getevents.2, io_setup.2, io_submit.2, ioctl_list.2, mkdir.2, mknod.2, pciconfig_read.2, pivot_root.2, posix_fadvise.2, query_module.2, sendfile.2, set_thread_area.2, setns.2, unshare.2, __setfpucw.3, a64l.3, addseverity.3, argz_add.3, bindresvport.3, cabs.3, cacos.3, cacosh.3, canonicalize_file_name.3, carg.3, casin.3, casinh.3, catan.3, catanh.3, ccos.3, ccosh.3, cerf.3, cexp.3, cexp2.3, cimag.3, clog.3, clog10.3, clog2.3, cmsg.3, conj.3, cpow.3, cproj.3, creal.3, csin.3, csinh.3, csqrt.3, ctan.3, ctanh.3, des_crypt.3, envz_add.3, fdim.3, fma.3, fmax.3, fmemopen.3, fmin.3, fmtmsg.3, fpclassify.3, gamma.3, getpt.3, getrpcent.3, getrpcport.3, getttyent.3, isgreater.3, key_setsecret.3, lgamma.3, malloc_hook.3, mempcpy.3, nan.3, netlink.3, nextafter.3, putgrent.3, remove.3, remquo.3, rpc.3, rtime.3, rtnetlink.3, setaliasent.3, setnetgrent.3, signbit.3, significand.3, sincos.3, stdin.3, tgamma.3, xcrypt.3, xdr.3, cciss.4, hpsa.4, mouse.4, pts.4, sk98lin.4, tty_ioctl.4, wavelan.4, hosts.equiv.5, rpc.5, tzfile.5, boot.7, complex.7, ddp.7, fifo.7, futex.7, icmp.7, ip.7, ipv6.7, netdevice.7, netlink.7, packet.7, raw.7, rtnetlink.7, socket.7, tcp.7, udp.7, unix.7, x25.7, sync.8: Global fix: Put copyright info at top of page, followed by blank line and LICENSE
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
2013-03-10 09:29:51 +00:00
|
|
|
.\"
|
getcpu.2, sendfile.2, cmsg.3, rtnetlink.3, arp.7, ddp.7, fifo.7, icmp.7, ip.7, ipv6.7, netdevice.7, packet.7, raw.7, rtnetlink.7, socket.7, tcp.7, udp.7, unix.7, x25.7: LICENSE_START(VERBATIM_ONE_PARA)
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
2013-03-10 09:29:00 +00:00
|
|
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.\" %%%LICENSE_START(VERBATIM_ONE_PARA)
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2008-08-08 16:41:48 +00:00
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.\" Permission is granted to distribute possibly modified copies
|
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|
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.\" of this page provided the header is included verbatim,
|
|
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.\" and in case of nontrivial modification author and date
|
|
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.\" of the modification is added to the header.
|
epoll_create.2, epoll_ctl.2, epoll_wait.2, eventfd.2, fallocate.2, futex.2, getcpu.2, getitimer.2, ioctl_list.2, ioprio_set.2, migrate_pages.2, move_pages.2, pciconfig_read.2, sendfile.2, setns.2, signalfd.2, spu_create.2, spu_run.2, sysinfo.2, timerfd_create.2, backtrace.3, cmsg.3, error.3, getpt.3, getrpcent.3, getrpcport.3, getsubopt.3, offsetof.3, program_invocation_name.3, rpc.3, rpmatch.3, rtnetlink.3, xdr.3, cciss.4, hpsa.4, pts.4, charmap.5, dir_colors.5, elf.5, gai.conf.5, locale.5, nscd.conf.5, nss.5, resolv.conf.5, rpc.5, arp.7, cpuset.7, ddp.7, epoll.7, fifo.7, futex.7, icmp.7, ip.7, ipv6.7, mailaddr.7, netdevice.7, packet.7, raw.7, regex.7, rtnetlink.7, socket.7, spufs.7, tcp.7, udp.7, unix.7, x25.7, ldconfig.8, nscd.8: Global fix: s/END_LICENSE/LICENSE_END/
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
2013-03-12 09:26:07 +00:00
|
|
|
.\" %%%LICENSE_END
|
networks.5, arp.7, cp1251.7, ddp.7, icmp.7, ip.7, ipv6.7, iso_8859-10.7, iso_8859-13.7, iso_8859-14.7, iso_8859-15.7, iso_8859-3.7, iso_8859-4.7, iso_8859-5.7, iso_8859-6.7, iso_8859-7.7, iso_8859-9.7, koi8-r.7, netdevice.7, netlink.7, packet.7, raw.7, rtnetlink.7, udp.7, x25.7, ld.so.8, sln.8, sync.8: srcfix
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
2013-03-12 11:28:50 +00:00
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.\"
|
2008-08-08 16:41:48 +00:00
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.\" $Id: udp.7,v 1.7 2000/01/22 01:55:05 freitag Exp $
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.\"
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2013-07-31 06:45:18 +00:00
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.TH UDP 7 2013-07-31 "Linux" "Linux Programmer's Manual"
|
2008-08-08 16:41:48 +00:00
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.SH NAME
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|
udp \- User Datagram Protocol for IPv4
|
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|
.SH SYNOPSIS
|
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.B #include <sys/socket.h>
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.br
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.B #include <netinet/in.h>
|
2013-07-26 14:58:45 +00:00
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.br
|
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|
.B #include <netinet/udp.h>
|
2008-08-08 16:41:48 +00:00
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.sp
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2008-08-08 16:47:53 +00:00
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.B udp_socket = socket(AF_INET, SOCK_DGRAM, 0);
|
2008-08-08 16:41:48 +00:00
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|
.SH DESCRIPTION
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This is an implementation of the User Datagram Protocol
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|
described in RFC\ 768.
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It implements a connectionless, unreliable datagram packet service.
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Packets may be reordered or duplicated before they arrive.
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UDP generates and checks checksums to catch transmission errors.
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When a UDP socket is created,
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its local and remote addresses are unspecified.
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|
Datagrams can be sent immediately using
|
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.BR sendto (2)
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or
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.BR sendmsg (2)
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with a valid destination address as an argument.
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|
When
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.BR connect (2)
|
2008-11-21 22:43:46 +00:00
|
|
|
is called on the socket, the default destination address is set and
|
2008-08-08 16:41:48 +00:00
|
|
|
datagrams can now be sent using
|
|
|
|
.BR send (2)
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or
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|
.BR write (2)
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|
|
without specifying a destination address.
|
|
|
|
It is still possible to send to other destinations by passing an
|
|
|
|
address to
|
|
|
|
.BR sendto (2)
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|
or
|
|
|
|
.BR sendmsg (2).
|
2008-11-21 22:43:46 +00:00
|
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|
In order to receive packets, the socket can be bound to a local
|
2008-08-08 16:41:48 +00:00
|
|
|
address first by using
|
|
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|
.BR bind (2).
|
time.1, get_kernel_syms.2, getitimer.2, open.2, perf_event_open.2, wait.2, alloca.3, bcmp.3, catopen.3, fputwc.3, iconv.3, iswalnum.3, iswalpha.3, iswblank.3, iswcntrl.3, iswctype.3, iswdigit.3, iswgraph.3, iswlower.3, iswprint.3, iswpunct.3, iswspace.3, iswupper.3, iswxdigit.3, mbsinit.3, putwchar.3, rcmd.3, rexec.3, sigqueue.3, strverscmp.3, wctrans.3, wctype.3, wcwidth.3, console_codes.4, initrd.4, st.4, elf.5, nss.5, ip.7, netdevice.7, path_resolution.7, socket.7, udp.7, ld.so.8: grfix: s/Otherwise /Otherwise, /
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
2014-04-28 08:15:47 +00:00
|
|
|
Otherwise, the socket layer will automatically assign
|
2008-08-08 16:41:48 +00:00
|
|
|
a free local port out of the range defined by
|
2009-09-28 08:42:15 +00:00
|
|
|
.I /proc/sys/net/ipv4/ip_local_port_range
|
2008-08-08 16:41:48 +00:00
|
|
|
and bind the socket to
|
|
|
|
.BR INADDR_ANY .
|
|
|
|
|
|
|
|
All receive operations return only one packet.
|
2008-11-21 22:43:46 +00:00
|
|
|
When the packet is smaller than the passed buffer, only that much
|
|
|
|
data is returned; when it is bigger, the packet is truncated and the
|
2008-08-08 16:41:48 +00:00
|
|
|
.B MSG_TRUNC
|
|
|
|
flag is set.
|
|
|
|
.B MSG_WAITALL
|
|
|
|
is not supported.
|
|
|
|
|
|
|
|
IP options may be sent or received using the socket options described in
|
|
|
|
.BR ip (7).
|
intro.1, _syscall.2, access.2, arch_prctl.2, cacheflush.2, chown.2, clock_getres.2, clone.2, create_module.2, fcntl.2, flock.2, get_kernel_syms.2, get_robust_list.2, get_thread_area.2, getcpu.2, getpriority.2, getrlimit.2, getrusage.2, ioprio_set.2, kexec_load.2, madvise.2, mbind.2, migrate_pages.2, mknod.2, mmap.2, mount.2, move_pages.2, mprotect.2, open.2, pause.2, pciconfig_read.2, perf_event_open.2, prctl.2, ptrace.2, query_module.2, read.2, reboot.2, recv.2, s390_runtime_instr.2, sched_setscheduler.2, select_tut.2, send.2, set_mempolicy.2, setfsgid.2, setfsuid.2, sigaction.2, spu_create.2, spu_run.2, stime.2, swapon.2, syslog.2, timer_create.2, timer_getoverrun.2, times.2, tkill.2, umount.2, unimplemented.2, ustat.2, vm86.2, wait.2, abs.3, aio_read.3, aio_write.3, bsd_signal.3, catgets.3, clearenv.3, cmsg.3, dbopen.3, dirfd.3, dlopen.3, exec.3, fenv.3, ferror.3, fmemopen.3, fnmatch.3, fopen.3, futimes.3, getaddrinfo.3, getifaddrs.3, getipnodebyname.3, hsearch.3, if_nameindex.3, inet_pton.3, mblen.3, mbrlen.3, mbsrtowcs.3, mbtowc.3, mcheck.3, memfrob.3, mq_notify.3, netlink.3, posix_memalign.3, printf.3, pthread_attr_setscope.3, pthread_cleanup_push.3, pthread_kill_other_threads_np.3, pthread_self.3, pthread_setcancelstate.3, pthread_setconcurrency.3, raise.3, resolver.3, rpc.3, rtime.3, rtnetlink.3, scanf.3, setbuf.3, setnetgrent.3, shm_open.3, sigpause.3, sigset.3, sigwait.3, sockatmark.3, strcasecmp.3, strcmp.3, strdup.3, strftime.3, strptime.3, strsignal.3, strverscmp.3, sysv_signal.3, termios.3, wcrtomb.3, wcsnlen.3, wcsnrtombs.3, wcsrtombs.3, wctomb.3, wprintf.3, console_codes.4, cpuid.4, msr.4, rtc.4, sk98lin.4, st.4, tty.4, charmap.5, core.5, elf.5, hosts.equiv.5, proc.5, resolv.conf.5, services.5, slabinfo.5, arp.7, bootparam.7, capabilities.7, charsets.7, cpuset.7, ddp.7, epoll.7, feature_test_macros.7, futex.7, hier.7, icmp.7, inotify.7, ip.7, ipv6.7, man-pages.7, mdoc.7, mdoc.samples.7, netdevice.7, netlink.7, numa.7, packet.7, path_resolution.7, posixoptions.7, pthreads.7, raw.7, rtld-audit.7, rtnetlink.7, sem_overview.7, sigevent.7, socket.7, spufs.7, tcp.7, udp.7, unicode.7, uri.7, utf-8.7, intro.8, ldconfig.8, sync.8: Global fix: fix placement of word "only"
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
2013-03-31 08:53:00 +00:00
|
|
|
They are processed by the kernel only when the appropriate
|
2009-09-28 08:42:15 +00:00
|
|
|
.I /proc
|
connect.2, listen.2, send.2, uname.2, cmsg.3, proc.5, arp.7, ddp.7, icmp.7, ip.7, raw.7, socket.7, tcp.7, udp.7: Global fix: eliminate mention of the obsolete sysctl(2) interface
Many pages still mention use of the obsolete sysctl(2) system
call, or used the term "sysctls"; rewrite these mentions to
instead be in terms of /proc interfaces.
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
2008-11-20 20:37:11 +00:00
|
|
|
parameter
|
2008-08-08 16:41:48 +00:00
|
|
|
is enabled (but still passed to the user even when it is turned off).
|
|
|
|
See
|
|
|
|
.BR ip (7).
|
|
|
|
|
|
|
|
When the
|
|
|
|
.B MSG_DONTROUTE
|
2008-11-21 22:38:34 +00:00
|
|
|
flag is set on sending, the destination address must refer to a local
|
intro.1, _syscall.2, access.2, arch_prctl.2, cacheflush.2, chown.2, clock_getres.2, clone.2, create_module.2, fcntl.2, flock.2, get_kernel_syms.2, get_robust_list.2, get_thread_area.2, getcpu.2, getpriority.2, getrlimit.2, getrusage.2, ioprio_set.2, kexec_load.2, madvise.2, mbind.2, migrate_pages.2, mknod.2, mmap.2, mount.2, move_pages.2, mprotect.2, open.2, pause.2, pciconfig_read.2, perf_event_open.2, prctl.2, ptrace.2, query_module.2, read.2, reboot.2, recv.2, s390_runtime_instr.2, sched_setscheduler.2, select_tut.2, send.2, set_mempolicy.2, setfsgid.2, setfsuid.2, sigaction.2, spu_create.2, spu_run.2, stime.2, swapon.2, syslog.2, timer_create.2, timer_getoverrun.2, times.2, tkill.2, umount.2, unimplemented.2, ustat.2, vm86.2, wait.2, abs.3, aio_read.3, aio_write.3, bsd_signal.3, catgets.3, clearenv.3, cmsg.3, dbopen.3, dirfd.3, dlopen.3, exec.3, fenv.3, ferror.3, fmemopen.3, fnmatch.3, fopen.3, futimes.3, getaddrinfo.3, getifaddrs.3, getipnodebyname.3, hsearch.3, if_nameindex.3, inet_pton.3, mblen.3, mbrlen.3, mbsrtowcs.3, mbtowc.3, mcheck.3, memfrob.3, mq_notify.3, netlink.3, posix_memalign.3, printf.3, pthread_attr_setscope.3, pthread_cleanup_push.3, pthread_kill_other_threads_np.3, pthread_self.3, pthread_setcancelstate.3, pthread_setconcurrency.3, raise.3, resolver.3, rpc.3, rtime.3, rtnetlink.3, scanf.3, setbuf.3, setnetgrent.3, shm_open.3, sigpause.3, sigset.3, sigwait.3, sockatmark.3, strcasecmp.3, strcmp.3, strdup.3, strftime.3, strptime.3, strsignal.3, strverscmp.3, sysv_signal.3, termios.3, wcrtomb.3, wcsnlen.3, wcsnrtombs.3, wcsrtombs.3, wctomb.3, wprintf.3, console_codes.4, cpuid.4, msr.4, rtc.4, sk98lin.4, st.4, tty.4, charmap.5, core.5, elf.5, hosts.equiv.5, proc.5, resolv.conf.5, services.5, slabinfo.5, arp.7, bootparam.7, capabilities.7, charsets.7, cpuset.7, ddp.7, epoll.7, feature_test_macros.7, futex.7, hier.7, icmp.7, inotify.7, ip.7, ipv6.7, man-pages.7, mdoc.7, mdoc.samples.7, netdevice.7, netlink.7, numa.7, packet.7, path_resolution.7, posixoptions.7, pthreads.7, raw.7, rtld-audit.7, rtnetlink.7, sem_overview.7, sigevent.7, socket.7, spufs.7, tcp.7, udp.7, unicode.7, uri.7, utf-8.7, intro.8, ldconfig.8, sync.8: Global fix: fix placement of word "only"
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
2013-03-31 08:53:00 +00:00
|
|
|
interface address and the packet is sent only to that interface.
|
2008-08-08 16:41:48 +00:00
|
|
|
|
2008-11-21 22:38:34 +00:00
|
|
|
By default, Linux UDP does path MTU (Maximum Transmission Unit) discovery.
|
2008-08-08 16:41:48 +00:00
|
|
|
This means the kernel
|
|
|
|
will keep track of the MTU to a specific target IP address and return
|
|
|
|
.B EMSGSIZE
|
|
|
|
when a UDP packet write exceeds it.
|
2008-11-21 22:43:46 +00:00
|
|
|
When this happens, the application should decrease the packet size.
|
2008-08-08 16:41:48 +00:00
|
|
|
Path MTU discovery can be also turned off using the
|
|
|
|
.B IP_MTU_DISCOVER
|
|
|
|
socket option or the
|
connect.2, listen.2, send.2, uname.2, cmsg.3, proc.5, arp.7, ddp.7, icmp.7, ip.7, raw.7, socket.7, tcp.7, udp.7: Global fix: eliminate mention of the obsolete sysctl(2) interface
Many pages still mention use of the obsolete sysctl(2) system
call, or used the term "sysctls"; rewrite these mentions to
instead be in terms of /proc interfaces.
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
2008-11-20 20:37:11 +00:00
|
|
|
.I /proc/sys/net/ipv4/ip_no_pmtu_disc
|
|
|
|
file; see
|
2008-08-08 16:41:48 +00:00
|
|
|
.BR ip (7)
|
|
|
|
for details.
|
2008-11-21 22:43:46 +00:00
|
|
|
When turned off, UDP will fragment outgoing UDP packets
|
2008-08-08 16:41:48 +00:00
|
|
|
that exceed the interface MTU.
|
2008-11-21 22:43:46 +00:00
|
|
|
However, disabling it is not recommended
|
2008-08-08 16:41:48 +00:00
|
|
|
for performance and reliability reasons.
|
intro.1, time.1, _syscall.2, accept.2, capget.2, clone.2, execve.2, fcntl.2, intro.2, ioctl_list.2, ioprio_set.2, kill.2, mlock.2, nanosleep.2, perf_event_open.2, select.2, stat.2, times.2, ustat.2, vfork.2, wait.2, cfree.3, dbopen.3, dlopen.3, fenv.3, fmtmsg.3, gamma.3, getaddrinfo.3, gethostbyname.3, getnameinfo.3, getspnam.3, login.3, printf.3, regex.3, stdio.3, sysconf.3, termios.3, ttyslot.3, undocumented.3, wordexp.3, console_codes.4, initrd.4, mouse.4, random.4, st.4, tty_ioctl.4, wavelan.4, charmap.5, dir_colors.5, hosts.5, termcap.5, armscii-8.7, boot.7, bootparam.7, capabilities.7, charsets.7, ddp.7, futex.7, glob.7, ipv6.7, iso_8859-1.7, iso_8859-10.7, iso_8859-11.7, iso_8859-13.7, iso_8859-14.7, iso_8859-15.7, iso_8859-16.7, iso_8859-2.7, iso_8859-3.7, iso_8859-4.7, iso_8859-5.7, iso_8859-6.7, iso_8859-7.7, iso_8859-8.7, iso_8859-9.7, koi8-r.7, koi8-u.7, man.7, numa.7, path_resolution.7, pipe.7, posixoptions.7, pthreads.7, pty.7, rtnetlink.7, signal.7, time.7, udp.7, udplite.7, unicode.7, uri.7, utf-8.7: G;lobal fix: remove unneeded double quotes in .SS headings
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
2013-02-24 18:02:18 +00:00
|
|
|
.SS Address format
|
2008-08-08 16:41:48 +00:00
|
|
|
UDP uses the IPv4
|
|
|
|
.I sockaddr_in
|
|
|
|
address format described in
|
|
|
|
.BR ip (7).
|
intro.1, time.1, _syscall.2, accept.2, capget.2, clone.2, execve.2, fcntl.2, intro.2, ioctl_list.2, ioprio_set.2, kill.2, mlock.2, nanosleep.2, perf_event_open.2, select.2, stat.2, times.2, ustat.2, vfork.2, wait.2, cfree.3, dbopen.3, dlopen.3, fenv.3, fmtmsg.3, gamma.3, getaddrinfo.3, gethostbyname.3, getnameinfo.3, getspnam.3, login.3, printf.3, regex.3, stdio.3, sysconf.3, termios.3, ttyslot.3, undocumented.3, wordexp.3, console_codes.4, initrd.4, mouse.4, random.4, st.4, tty_ioctl.4, wavelan.4, charmap.5, dir_colors.5, hosts.5, termcap.5, armscii-8.7, boot.7, bootparam.7, capabilities.7, charsets.7, ddp.7, futex.7, glob.7, ipv6.7, iso_8859-1.7, iso_8859-10.7, iso_8859-11.7, iso_8859-13.7, iso_8859-14.7, iso_8859-15.7, iso_8859-16.7, iso_8859-2.7, iso_8859-3.7, iso_8859-4.7, iso_8859-5.7, iso_8859-6.7, iso_8859-7.7, iso_8859-8.7, iso_8859-9.7, koi8-r.7, koi8-u.7, man.7, numa.7, path_resolution.7, pipe.7, posixoptions.7, pthreads.7, pty.7, rtnetlink.7, signal.7, time.7, udp.7, udplite.7, unicode.7, uri.7, utf-8.7: G;lobal fix: remove unneeded double quotes in .SS headings
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
2013-02-24 18:02:18 +00:00
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.SS Error handling
|
2008-08-08 16:41:48 +00:00
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All fatal errors will be passed to the user as an error return even
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when the socket is not connected.
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This includes asynchronous errors
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received from the network.
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You may get an error for an earlier packet
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that was sent on the same socket.
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This behavior differs from many other BSD socket implementations
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which don't pass any errors unless the socket is connected.
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Linux's behavior is mandated by
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.BR RFC\ 1122 .
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2008-11-21 22:43:46 +00:00
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For compatibility with legacy code, in Linux 2.0 and 2.2
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2008-08-08 16:41:48 +00:00
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it was possible to set the
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.B SO_BSDCOMPAT
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.B SOL_SOCKET
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option to receive remote errors only when the socket has been
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connected (except for
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.B EPROTO
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and
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.BR EMSGSIZE ).
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Locally generated errors are always passed.
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Support for this socket option was removed in later kernels; see
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.BR socket (7)
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for further information.
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When the
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.B IP_RECVERR
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2008-11-21 22:43:46 +00:00
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option is enabled, all errors are stored in the socket error queue,
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2008-08-08 16:41:48 +00:00
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and can be received by
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.BR recvmsg (2)
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with the
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.B MSG_ERRQUEUE
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flag set.
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2008-11-21 23:02:06 +00:00
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.SS /proc interfaces
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System-wide UDP parameter settings can be accessed by files in the directory
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.IR /proc/sys/net/ipv4/ .
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.TP
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.IR udp_mem " (since Linux 2.6.25)"
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This is a vector of three integers governing the number
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of pages allowed for queueing by all UDP sockets.
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.RS
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.TP 10
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.I min
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Below this number of pages, UDP is not bothered about its
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memory appetite.
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When the amount of memory allocated by UDP exceeds
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this number, UDP starts to moderate memory usage.
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.TP
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.I pressure
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This value was introduced to follow the format of
|
2008-11-26 02:44:53 +00:00
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.IR tcp_mem
|
2008-11-21 23:02:06 +00:00
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(see
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.BR tcp (7)).
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.TP
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.I max
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Number of pages allowed for queueing by all UDP sockets.
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.RE
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.IP
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Defaults values for these three items are
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calculated at boot time from the amount of available memory.
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.TP
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.IR udp_rmem_min " (integer; default value: PAGE_SIZE; since Linux 2.6.25)"
|
2009-09-27 07:26:40 +00:00
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Minimal size, in bytes, of receive buffers used by UDP sockets in moderation.
|
2008-11-21 23:02:06 +00:00
|
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|
Each UDP socket is able to use the size for receiving data,
|
2009-09-27 07:26:40 +00:00
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even if total pages of UDP sockets exceed
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|
|
|
.I udp_mem
|
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|
|
pressure.
|
2008-11-21 23:02:06 +00:00
|
|
|
.TP
|
|
|
|
.IR udp_wmem_min " (integer; default value: PAGE_SIZE; since Linux 2.6.25)"
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|
Minimal size, in bytes, of send buffer used by UDP sockets in moderation.
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Each UDP socket is able to use the size for sending data,
|
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|
even if total pages of UDP sockets exceed
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|
|
|
.I udp_mem
|
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|
|
pressure.
|
intro.1, time.1, _syscall.2, accept.2, capget.2, clone.2, execve.2, fcntl.2, intro.2, ioctl_list.2, ioprio_set.2, kill.2, mlock.2, nanosleep.2, perf_event_open.2, select.2, stat.2, times.2, ustat.2, vfork.2, wait.2, cfree.3, dbopen.3, dlopen.3, fenv.3, fmtmsg.3, gamma.3, getaddrinfo.3, gethostbyname.3, getnameinfo.3, getspnam.3, login.3, printf.3, regex.3, stdio.3, sysconf.3, termios.3, ttyslot.3, undocumented.3, wordexp.3, console_codes.4, initrd.4, mouse.4, random.4, st.4, tty_ioctl.4, wavelan.4, charmap.5, dir_colors.5, hosts.5, termcap.5, armscii-8.7, boot.7, bootparam.7, capabilities.7, charsets.7, ddp.7, futex.7, glob.7, ipv6.7, iso_8859-1.7, iso_8859-10.7, iso_8859-11.7, iso_8859-13.7, iso_8859-14.7, iso_8859-15.7, iso_8859-16.7, iso_8859-2.7, iso_8859-3.7, iso_8859-4.7, iso_8859-5.7, iso_8859-6.7, iso_8859-7.7, iso_8859-8.7, iso_8859-9.7, koi8-r.7, koi8-u.7, man.7, numa.7, path_resolution.7, pipe.7, posixoptions.7, pthreads.7, pty.7, rtnetlink.7, signal.7, time.7, udp.7, udplite.7, unicode.7, uri.7, utf-8.7: G;lobal fix: remove unneeded double quotes in .SS headings
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
2013-02-24 18:02:18 +00:00
|
|
|
.SS Socket options
|
2008-08-08 16:41:48 +00:00
|
|
|
To set or get a UDP socket option, call
|
|
|
|
.BR getsockopt (2)
|
|
|
|
to read or
|
|
|
|
.BR setsockopt (2)
|
|
|
|
to write the option with the option level argument set to
|
|
|
|
.BR IPPROTO_UDP .
|
2013-04-18 14:15:21 +00:00
|
|
|
Unless otherwise noted,
|
|
|
|
.I optval
|
|
|
|
is a pointer to an
|
|
|
|
.IR int .
|
2008-08-08 16:41:48 +00:00
|
|
|
.TP
|
|
|
|
.BR UDP_CORK " (since Linux 2.5.44)"
|
|
|
|
If this option is enabled, then all data output on this socket
|
|
|
|
is accumulated into a single datagram that is transmitted when
|
|
|
|
the option is disabled.
|
|
|
|
This option should not be used in code intended to be
|
|
|
|
portable.
|
|
|
|
.\" FIXME document UDP_ENCAP (new in kernel 2.5.67)
|
2008-11-21 22:33:24 +00:00
|
|
|
.\" From include/linux/udp.h:
|
|
|
|
.\" /* UDP encapsulation types */
|
|
|
|
.\" #define UDP_ENCAP_ESPINUDP_NON_IKE 1 /* draft-ietf-ipsec-nat-t-ike-00/01 */
|
|
|
|
.\" #define UDP_ENCAP_ESPINUDP 2 /* draft-ietf-ipsec-udp-encaps-06 */
|
|
|
|
.\" #define UDP_ENCAP_L2TPINUDP 3 /* rfc2661 */
|
2008-08-08 16:41:48 +00:00
|
|
|
.SS Ioctls
|
|
|
|
These ioctls can be accessed using
|
|
|
|
.BR ioctl (2).
|
|
|
|
The correct syntax is:
|
|
|
|
.PP
|
|
|
|
.RS
|
|
|
|
.nf
|
|
|
|
.BI int " value";
|
|
|
|
.IB error " = ioctl(" udp_socket ", " ioctl_type ", &" value ");"
|
|
|
|
.fi
|
|
|
|
.RE
|
|
|
|
.TP
|
|
|
|
.BR FIONREAD " (" SIOCINQ )
|
|
|
|
Gets a pointer to an integer as argument.
|
|
|
|
Returns the size of the next pending datagram in the integer in bytes,
|
|
|
|
or 0 when no datagram is pending.
|
2010-06-13 03:00:58 +00:00
|
|
|
.B Warning:
|
|
|
|
Using
|
|
|
|
.BR FIONREAD ,
|
|
|
|
it is impossible to distinguish the case where no datagram is pending
|
|
|
|
from the case where the next pending datagram contains zero bytes of data.
|
|
|
|
It is safer to use
|
|
|
|
.BR select (2),
|
|
|
|
.BR poll (2),
|
|
|
|
or
|
|
|
|
.BR epoll (7)
|
|
|
|
to distinguish these cases.
|
|
|
|
.\" See http://www.securiteam.com/unixfocus/5KP0I15IKO.html
|
|
|
|
.\" "GNUnet DoS (UDP Socket Unreachable)", 14 May 2006
|
2008-08-08 16:41:48 +00:00
|
|
|
.TP
|
|
|
|
.BR TIOCOUTQ " (" SIOCOUTQ )
|
|
|
|
Returns the number of data bytes in the local send queue.
|
|
|
|
Only supported with Linux 2.4 and above.
|
|
|
|
.PP
|
2014-01-10 17:21:00 +00:00
|
|
|
In addition, all ioctls documented in
|
2008-08-08 16:41:48 +00:00
|
|
|
.BR ip (7)
|
|
|
|
and
|
|
|
|
.BR socket (7)
|
|
|
|
are supported.
|
|
|
|
.SH ERRORS
|
|
|
|
All errors documented for
|
|
|
|
.BR socket (7)
|
|
|
|
or
|
|
|
|
.BR ip (7)
|
|
|
|
may be returned by a send or receive on a UDP socket.
|
2008-12-01 15:21:23 +00:00
|
|
|
.TP
|
2008-08-08 16:41:48 +00:00
|
|
|
.B ECONNREFUSED
|
|
|
|
No receiver was associated with the destination address.
|
|
|
|
This might be caused by a previous packet sent over the socket.
|
|
|
|
.SH VERSIONS
|
2008-11-21 22:36:31 +00:00
|
|
|
.B IP_RECVERR
|
|
|
|
is a new feature in Linux 2.2.
|
2008-08-08 16:41:48 +00:00
|
|
|
.\" .SH CREDITS
|
|
|
|
.\" This man page was written by Andi Kleen.
|
getent.1, intro.1, time.1, _exit.2, _syscall.2, accept.2, access.2, acct.2, adjtimex.2, alarm.2, alloc_hugepages.2, arch_prctl.2, bdflush.2, bind.2, brk.2, cacheflush.2, capget.2, chdir.2, chmod.2, chown.2, chroot.2, clock_getres.2, clock_nanosleep.2, clone.2, close.2, connect.2, create_module.2, delete_module.2, dup.2, epoll_create.2, epoll_ctl.2, epoll_wait.2, eventfd.2, execve.2, exit_group.2, faccessat.2, fchmodat.2, fchownat.2, fcntl.2, flock.2, fork.2, fstatat.2, fsync.2, futex.2, futimesat.2, get_kernel_syms.2, get_robust_list.2, get_thread_area.2, getcpu.2, getdents.2, getdomainname.2, getgid.2, getgroups.2, gethostname.2, getitimer.2, getpagesize.2, getpeername.2, getpid.2, getpriority.2, getresuid.2, getrlimit.2, getrusage.2, getsid.2, getsockname.2, getsockopt.2, gettid.2, gettimeofday.2, getuid.2, getunwind.2, getxattr.2, idle.2, init_module.2, inotify_add_watch.2, inotify_init.2, inotify_rm_watch.2, intro.2, io_cancel.2, io_destroy.2, io_getevents.2, io_setup.2, io_submit.2, ioctl.2, ioctl_list.2, ioperm.2, iopl.2, ioprio_set.2, ipc.2, kcmp.2, kill.2, killpg.2, link.2, linkat.2, listen.2, listxattr.2, llseek.2, lookup_dcookie.2, lseek.2, madvise.2, migrate_pages.2, mincore.2, mkdir.2, mkdirat.2, mknod.2, mknodat.2, mlock.2, mmap.2, mmap2.2, modify_ldt.2, mount.2, move_pages.2, mprotect.2, mq_getsetattr.2, mremap.2, msgctl.2, msgget.2, msgop.2, msync.2, nanosleep.2, nfsservctl.2, nice.2, open.2, openat.2, outb.2, pause.2, pciconfig_read.2, perf_event_open.2, perfmonctl.2, personality.2, pipe.2, pivot_root.2, poll.2, posix_fadvise.2, prctl.2, pread.2, process_vm_readv.2, ptrace.2, query_module.2, quotactl.2, read.2, readahead.2, readdir.2, readlink.2, readlinkat.2, readv.2, reboot.2, recv.2, remap_file_pages.2, removexattr.2, rename.2, renameat.2, rmdir.2, rt_sigqueueinfo.2, sched_get_priority_max.2, sched_rr_get_interval.2, sched_setaffinity.2, sched_setparam.2, sched_setscheduler.2, sched_yield.2, select.2, semctl.2, semget.2, semop.2, send.2, sendfile.2, set_thread_area.2, set_tid_address.2, seteuid.2, setfsgid.2, setfsuid.2, setgid.2, setpgid.2, setresuid.2, setreuid.2, setsid.2, setuid.2, setup.2, setxattr.2, shmctl.2, shmget.2, shmop.2, shutdown.2, sigaction.2, sigaltstack.2, signal.2, signalfd.2, sigpending.2, sigprocmask.2, sigreturn.2, sigsuspend.2, sigwaitinfo.2, socket.2, socketcall.2, socketpair.2, splice.2, stat.2, statfs.2, stime.2, swapon.2, symlink.2, symlinkat.2, sync.2, sync_file_range.2, sysctl.2, sysfs.2, sysinfo.2, syslog.2, tee.2, time.2, timerfd_create.2, times.2, tkill.2, truncate.2, umask.2, umount.2, uname.2, unimplemented.2, unlink.2, unlinkat.2, uselib.2, ustat.2, utime.2, utimensat.2, vfork.2, vhangup.2, vm86.2, vmsplice.2, wait.2, wait4.2, write.2, CPU_SET.3, INFINITY.3, MB_CUR_MAX.3, MB_LEN_MAX.3, __setfpucw.3, a64l.3, abort.3, abs.3, acos.3, acosh.3, addseverity.3, adjtime.3, aio_cancel.3, aio_error.3, aio_fsync.3, aio_read.3, aio_return.3, aio_suspend.3, aio_write.3, alloca.3, argz_add.3, asin.3, asinh.3, asprintf.3, assert.3, assert_perror.3, atan.3, atan2.3, atanh.3, atexit.3, atof.3, atoi.3, backtrace.3, basename.3, bcmp.3, bcopy.3, bindresvport.3, bsd_signal.3, bsearch.3, bstring.3, btowc.3, btree.3, byteorder.3, bzero.3, cabs.3, cacos.3, cacosh.3, canonicalize_file_name.3, carg.3, casin.3, casinh.3, catan.3, catanh.3, catgets.3, catopen.3, cbrt.3, ccos.3, ccosh.3, ceil.3, cerf.3, cexp.3, cexp2.3, cfree.3, cimag.3, clearenv.3, clock.3, clock_getcpuclockid.3, clog.3, clog10.3, clog2.3, closedir.3, cmsg.3, confstr.3, conj.3, copysign.3, cos.3, cosh.3, cpow.3, cproj.3, creal.3, crypt.3, csin.3, csinh.3, csqrt.3, ctan.3, ctanh.3, ctermid.3, ctime.3, daemon.3, dbopen.3, des_crypt.3, difftime.3, dirfd.3, div.3, dl_iterate_phdr.3, dlopen.3, dprintf.3, drand48.3, drand48_r.3, dysize.3, ecvt.3, ecvt_r.3, encrypt.3, end.3, endian.3, envz_add.3, erf.3, erfc.3, err.3, errno.3, error.3, ether_aton.3, euidaccess.3, exec.3, exit.3, exp.3, exp10.3, exp2.3, expm1.3, fabs.3, fclose.3, fcloseall.3, fdim.3, fenv.3, ferror.3, fexecve.3, fflush.3, ffs.3, fgetgrent.3, fgetpwent.3, fgetwc.3, fgetws.3, finite.3, flockfile.3, floor.3, fma.3, fmax.3, fmemopen.3, fmin.3, fmod.3, fmtmsg.3, fnmatch.3, fopen.3, fpathconf.3, fpclassify.3, fpurge.3, fputwc.3, fputws.3, fread.3, frexp.3, fseek.3, fseeko.3, ftime.3, ftok.3, fts.3, ftw.3, futimes.3, fwide.3, gamma.3, gcvt.3, getaddrinfo.3, getaddrinfo_a.3, getauxval.3, getcontext.3, getcwd.3, getdate.3, getdirentries.3, getdtablesize.3, getenv.3, getfsent.3, getgrent.3, getgrent_r.3, getgrnam.3, getgrouplist.3, gethostbyname.3, gethostid.3, getipnodebyname.3, getline.3, getloadavg.3, getlogin.3, getmntent.3, getnameinfo.3, getnetent.3, getnetent_r.3, getopt.3, getpass.3, getprotoent.3, getprotoent_r.3, getpt.3, getpw.3, getpwent.3, getpwent_r.3, getpwnam.3, getrpcent.3, getrpcent_r.3, getrpcport.3, gets.3, getservent.3, getservent_r.3, getspnam.3, getttyent.3, getumask.3, getusershell.3, getutent.3, getw.3, getwchar.3, glob.3, grantpt.3, gsignal.3, hash.3, hsearch.3, hypot.3, iconv.3, iconv_close.3, iconv_open.3, ilogb.3, index.3, inet.3, inet_ntop.3, inet_pton.3, infnan.3, initgroups.3, insque.3, intro.3, isalpha.3, isatty.3, isgreater.3, iswalnum.3, iswalpha.3, iswblank.3, iswcntrl.3, iswctype.3, iswdigit.3, iswgraph.3, iswlower.3, iswprint.3, iswpunct.3, iswspace.3, iswupper.3, iswxdigit.3, j0.3, key_setsecret.3, ldexp.3, lgamma.3, lio_listio.3, localeconv.3, lockf.3, log.3, log10.3, log1p.3, log2.3, logb.3, login.3, longjmp.3, lrint.3, lround.3, lsearch.3, lseek64.3, makecontext.3, makedev.3, malloc.3, malloc_hook.3, mblen.3, mbrlen.3, mbrtowc.3, mbsinit.3, mbsnrtowcs.3, mbsrtowcs.3, mbstowcs.3, mbtowc.3, memccpy.3, memchr.3, memcmp.3, memcpy.3, memfrob.3, memmem.3, memmove.3, mempcpy.3, memset.3, mkdtemp.3, mkfifo.3, mkfifoat.3, mkstemp.3, mktemp.3, modf.3, mpool.3, mq_close.3, mq_getattr.3, mq_notify.3, mq_open.3, mq_receive.3, mq_send.3, mq_unlink.3, mtrace.3, nan.3, netlink.3, nextafter.3, nl_langinfo.3, offsetof.3, on_exit.3, opendir.3, openpty.3, perror.3, popen.3, posix_fallocate.3, posix_memalign.3, posix_openpt.3, pow.3, pow10.3, printf.3, profil.3, program_invocation_name.3, psignal.3, pthread_kill_other_threads_np.3, ptsname.3, putenv.3, putgrent.3, putpwent.3, puts.3, putwchar.3, qecvt.3, qsort.3, queue.3, raise.3, rand.3, random.3, random_r.3, rcmd.3, re_comp.3, readdir.3, realpath.3, recno.3, regex.3, remainder.3, remove.3, remquo.3, resolver.3, rewinddir.3, rexec.3, rint.3, round.3, rpc.3, rpmatch.3, rtime.3, rtnetlink.3, scalb.3, scalbln.3, scandir.3, scandirat.3, scanf.3, seekdir.3, sem_close.3, sem_destroy.3, sem_getvalue.3, sem_init.3, sem_open.3, sem_post.3, sem_unlink.3, sem_wait.3, setaliasent.3, setbuf.3, setenv.3, setjmp.3, setlocale.3, setlogmask.3, setnetgrent.3, shm_open.3, siginterrupt.3, signbit.3, significand.3, sigpause.3, sigqueue.3, sigset.3, sigsetops.3, sigvec.3, sin.3, sincos.3, sinh.3, sleep.3, sockatmark.3, sqrt.3, statvfs.3, stdarg.3, stdin.3, stdio.3, stdio_ext.3, stpcpy.3, stpncpy.3, strcasecmp.3, strcat.3, strchr.3, strcmp.3, strcoll.3, strcpy.3, strdup.3, strerror.3, strfmon.3, strfry.3, strftime.3, string.3, strlen.3, strnlen.3, strpbrk.3, strptime.3, strsep.3, strsignal.3, strspn.3, strstr.3, strtod.3, strtoimax.3, strtok.3, strtol.3, strtoul.3, strverscmp.3, strxfrm.3, swab.3, sysconf.3, syslog.3, system.3, sysv_signal.3, tan.3, tanh.3, tcgetpgrp.3, tcgetsid.3, telldir.3, tempnam.3, termios.3, tgamma.3, timegm.3, timeradd.3, tmpfile.3, tmpnam.3, toascii.3, toupper.3, towctrans.3, towlower.3, towupper.3, trunc.3, tsearch.3, ttyname.3, ttyslot.3, tzset.3, ualarm.3, ulimit.3, ungetwc.3, unlocked_stdio.3, unlockpt.3, updwtmp.3, usleep.3, wcpcpy.3, wcpncpy.3, wcrtomb.3, wcscasecmp.3, wcscat.3, wcschr.3, wcscmp.3, wcscpy.3, wcscspn.3, wcsdup.3, wcslen.3, wcsncasecmp.3, wcsncat.3, wcsncmp.3, wcsncpy.3, wcsnlen.3, wcsnrtombs.3, wcspbrk.3, wcsrchr.3, wcsrtombs.3, wcsspn.3, wcsstr.3, wcstoimax.3, wcstok.3, wcstombs.3, wcswidth.3, wctob.3, wctomb.3, wctrans.3, wctype.3, wcwidth.3, wmemchr.3, wmemcmp.3, wmemcpy.3, wmemmove.3, wmemset.3, wordexp.3, wprintf.3, xcrypt.3, xdr.3, y0.3, cciss.4, console.4, console_codes.4, console_ioctl.4, dsp56k.4, fd.4, full.4, hd.4, hpsa.4, initrd.4, intro.4, lp.4, mem.4, mouse.4, null.4, pts.4, ram.4, random.4, rtc.4, sk98lin.4, st.4, tty.4, ttyS.4, tty_ioctl.4, vcs.4, wavelan.4, acct.5, charmap.5, dir_colors.5, filesystems.5, ftpusers.5, group.5, host.conf.5, hosts.5, hosts.equiv.5, intro.5, issue.5, locale.5, motd.5, networks.5, nologin.5, nscd.conf.5, passwd.5, proc.5, protocols.5, resolv.conf.5, rpc.5, securetty.5, services.5, shells.5, termcap.5, ttytype.5, utmp.5, armscii-8.7, arp.7, ascii.7, bootparam.7, capabilities.7, charsets.7, complex.7, cp1251.7, credentials.7, ddp.7, environ.7, epoll.7, fifo.7, futex.7, glob.7, hier.7, icmp.7, inotify.7, intro.7, ip.7, ipv6.7, iso_8859-1.7, iso_8859-10.7, iso_8859-11.7, iso_8859-13.7, iso_8859-14.7, iso_8859-15.7, iso_8859-16.7, iso_8859-2.7, iso_8859-3.7, iso_8859-4.7, iso_8859-5.7, iso_8859-6.7, iso_8859-7.7, iso_8859-8.7, iso_8859-9.7, koi8-r.7, koi8-u.7, locale.7, mailaddr.7, man.7, mq_overview.7, netdevice.7, netlink.7, numa.7, packet.7, path_resolution.7, pipe.7, posixoptions.7, pthreads.7, pty.7, raw.7, regex.7, rtld-audit.7, rtnetlink.7, sem_overview.7, shm_overview.7, sigevent.7, signal.7, socket.7, standards.7, suffixes.7, svipc.7, tcp.7, termio.7, time.7, udp.7, udplite.7, unicode.7, unix.7, uri.7, utf-8.7, x25.7, nscd.8, sync.8, tzselect.8, zdump.8, zic.8: Global fix: remove unneeded double quotes in .SH headings
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
2013-02-24 18:01:36 +00:00
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.SH SEE ALSO
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2008-08-08 16:41:48 +00:00
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.BR ip (7),
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.BR raw (7),
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2008-08-08 16:50:10 +00:00
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.BR socket (7),
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.BR udplite (7)
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2008-08-08 16:41:48 +00:00
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RFC\ 768 for the User Datagram Protocol.
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.br
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RFC\ 1122 for the host requirements.
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.br
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RFC\ 1191 for a description of path MTU discovery.
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