Fix the description of "pcap_dispatch()" and "pcap_loop()" to reflect

reality ("pcap_dispatch()", on a live capture, never reads more than one
bufferful of packets).

Break the description of "pcap_dispatch()" into multiple paragraphs.

Move the description of "pcap_loop()" right after the descriptionof
"pcap_dispatch()", and note that "pcap_dump()" can be used as the
callback function for either of them.

diff --git a/pcap.3 b/pcap.3
index 097873613f1747cddd134ab1068178aa32783151..03f8f7a769070cd4f650b3ff8181578dc09322c7 100644 (file)
--- a/pcap.3
+++ b/pcap.3
@@ -1,4 +1,4 @@
-.\" @(#) $Header: /tcpdump/master/libpcap/Attic/pcap.3,v 1.15 2000-12-28 01:58:05 guy Exp $
+.\" @(#) $Header: /tcpdump/master/libpcap/Attic/pcap.3,v 1.16 2001-01-03 00:57:56 guy Exp $

 .\"
 .\" Copyright (c) 1994, 1996, 1997
 .\"    The Regents of the University of California.  All rights reserved.
 .\"
 .\" Copyright (c) 1994, 1996, 1997
 .\"    The Regents of the University of California.  All rights reserved.


@@ -201,32 +201,22 @@ and
 are
 .I bpf_u_int32
 pointers.
 are
 .I bpf_u_int32
 pointers.

-A return of -1 indicates an error in which case
+A return of \-1 indicates an error in which case

 .I errbuf
 is filled in with an appropriate error message.
 .PP
 .B pcap_dispatch()
 is used to collect and process packets.
 .I cnt
 .I errbuf
 is filled in with an appropriate error message.
 .PP
 .B pcap_dispatch()
 is used to collect and process packets.
 .I cnt

-specifies the maximum number of packets to process before returning. A
+specifies the maximum number of packets to process before returning.
+This is not a minimum number; when reading a live capture, only one
+bufferful of packets is read at a time, so fewer than

 .I cnt
 .I cnt

-of -1 processes all the packets received in one buffer. A
+packets may be processed. A

 .I cnt
 .I cnt

-of 0 processes all packets until an error occurs,
-.B EOF
-is reached, or, on some platforms, the read times out (when doing live
-reads and a non-zero read timeout is specified).
-.B pcap_dispatch()
-will not necessarily return when the read times out; on some platforms,
-the read timeout isn't supported, and, on other platforms, the timer
-doesn't start until at least one packet arrives.  This means that the
-read timeout should
-.B NOT
-be used in, for example, an interactive application, to allow the packet
-capture loop to ``poll'' for user input periodically, as there's no
-guarantee that
-.B pcap_dispatch()
-will return after the timeout expires.
+of \-1 processes all the packets received in one buffer when reading a
+live capture, or all the packets in the file when reading a
+``savefile''.

 .I callback
 specifies a routine to be called with three arguments:
 a
 .I callback
 specifies a routine to be called with three arguments:
 a


@@ -238,21 +228,69 @@ a pointer to the
 struct (which precede the actual network headers and data),
 and a
 .I u_char
 struct (which precede the actual network headers and data),
 and a
 .I u_char

-pointer to the packet data. The number of packets read is returned.
-Zero is returned when
-.B EOF
-is reached in a ``savefile.'' A return of -1 indicates
+pointer to the packet data.
+.PP
+The number of packets read is returned.
+0 is returned if no packets were read from a live capture (if, for
+example, they were discarded because they didn't pass the packet filter,
+or if, on platforms that support a read timeout that starts before any
+packets arrive, the timeout expires before any packets arrive, or if the
+file descriptor for the capture device is in non-blocking mode and no
+packets were available to be read) or if no more packets are available
+in a ``savefile.'' A return of \-1 indicates

 an error in which case
 .B pcap_perror()
 or
 .B pcap_geterr()
 may be used to display the error text.
 .PP
 an error in which case
 .B pcap_perror()
 or
 .B pcap_geterr()
 may be used to display the error text.
 .PP

+.BR NOTE :
+when reading a live capture,
+.B pcap_dispatch()
+will not necessarily return when the read times out; on some platforms,
+the read timeout isn't supported, and, on other platforms, the timer
+doesn't start until at least one packet arrives.  This means that the
+read timeout should
+.B NOT
+be used in, for example, an interactive application, to allow the packet
+capture loop to ``poll'' for user input periodically, as there's no
+guarantee that
+.B pcap_dispatch()
+will return after the timeout expires.
+.PP
+.B pcap_loop()
+is similar to
+.B pcap_dispatch()
+except it keeps reading packets until
+.I cnt
+packets are processed or an error occurs.
+It does
+.B not
+return when live read timeouts occur.
+Rather, specifying a non-zero read timeout to
+.B pcap_open_live()
+and then calling
+.B pcap_dispatch()
+allows the reception and processing of any packets that arrive when the
+timeout occurs.
+A negative
+.I cnt
+causes
+.B pcap_loop()
+to loop forever (or at least until an error occurs).
+.PP
+.B pcap_next()
+returns a
+.I u_char
+pointer to the next packet.
+.PP

 .B pcap_dump()
 outputs a packet to the ``savefile'' opened with
 .BR pcap_dump_open() .
 Note that its calling arguments are suitable for use with
 .B pcap_dump()
 outputs a packet to the ``savefile'' opened with
 .BR pcap_dump_open() .
 Note that its calling arguments are suitable for use with

-.BR pcap_dispatch() .
+.B pcap_dispatch()
+or
+.BR pcap_loop() .

 .PP
 .B pcap_compile()
 is used to compile the string
 .PP
 .B pcap_compile()
 is used to compile the string


@@ -267,7 +305,7 @@ struct and is filled in by
 controls whether optimization on the resulting code is performed.
 .I netmask
 specifies the netmask of the local net.
 controls whether optimization on the resulting code is performed.
 .I netmask
 specifies the netmask of the local net.

-A return of -1 indicates an error in which case
+A return of \-1 indicates an error in which case

 .BR pcap_geterr()
 may be used to display the error text.
 .PP
 .BR pcap_geterr()
 may be used to display the error text.
 .PP


@@ -279,7 +317,7 @@ snaplen and linktype explicitly.  It is intended to be used for
 compiling filters for direct BPF usage, without necessarily having
 called
 .BR pcap_open() .
 compiling filters for direct BPF usage, without necessarily having
 called
 .BR pcap_open() .

-A return of -1 indicates an error; the error text is unavailable.
+A return of \-1 indicates an error; the error text is unavailable.

 .RB ( pcap_compile_nopcap()
 is a wrapper around
 .BR pcap_open_dead() ,
 .RB ( pcap_compile_nopcap()
 is a wrapper around
 .BR pcap_open_dead() ,


@@ -313,32 +351,6 @@ when that BPF program is no longer needed, for example after it
 has been made the filter program for a pcap structure by a call to
 .BR pcap_setfilter() .
 .PP
 has been made the filter program for a pcap structure by a call to
 .BR pcap_setfilter() .
 .PP

-.B pcap_loop()
-is similar to
-.B pcap_dispatch()
-except it keeps reading packets until
-.I cnt
-packets are processed or an error occurs.
-It does
-.B not
-return when live read timeouts occur.
-Rather, specifying a non-zero read timeout to
-.B pcap_open_live()
-and then calling
-.B pcap_dispatch()
-allows the reception and processing of any packets that arrive when the
-timeout occurs.
-A negative
-.I cnt
-causes
-.B pcap_loop()
-to loop forever (or at least until an error occurs).
-.PP
-.B pcap_next()
-returns a
-.I u_char
-pointer to the next packet.
-.PP

 .B pcap_datalink()
 returns the link layer type, e.g.
 .BR DLT_EN10MB .
 .B pcap_datalink()
 returns the link layer type, e.g.
 .BR DLT_EN10MB .


@@ -368,7 +380,7 @@ returns 0 and fills in a
 .B pcap_stat
 struct. The values represent packet statistics from the start of the
 run to the time of the call. If there is an error or the under lying
 .B pcap_stat
 struct. The values represent packet statistics from the start of the
 run to the time of the call. If there is an error or the under lying

-packet capture doesn't support packet statistics, -1 is returned and
+packet capture doesn't support packet statistics, \-1 is returned and

 the error text can be obtained with
 .B pcap_perror()
 or
 the error text can be obtained with
 .B pcap_perror()
 or