svn commit: r187935 - head/share/man/man4

[Giorgos Keramidas]

Author: keramida (doc committer)
Date: Fri Jan 30 19:33:04 2009
New Revision: 187935
URL: http://svn.freebsd.org/changeset/base/187935

Log:
  Sometimes, depending on the bpf filter rules used in $PATTERN,
  the example script of the manpage feeds awk(1) with values larger
  than UINT32_MAX.  Then awk prints a negative value, and this
  messes up $BPFPROG.  Trying to load the resulting bpf byte codes
  with ngctl then fails.
  
  For example, the output for PATTERN="udp and dst net 255.255.0.0/16"
  should be (all in one line):
  
      bpf_prog_len=10
      bpf_prog=[
        { code=40 jt=0 jf=0 k=12 }
        { code=21 jt=7 jf=0 k=34525 }
        { code=21 jt=0 jf=6 k=2048 }
        { code=48 jt=0 jf=0 k=23 }
        { code=21 jt=0 jf=4 k=17 }
        { code=32 jt=0 jf=0 k=30 }
        { code=84 jt=0 jf=0 k=4294901760 }
        { code=21 jt=0 jf=1 k=4294901760 }
        { code=6 jt=0 jf=0 k=8192 }
        { code=6 jt=0 jf=0 k=0 }
      ]
  
  The two k=4294901760 values are displayed as k=-2147483648 by awk.
  
  Replace the awk script of the manpage example with a slower but
  safer version, that doesn't really attempt to convert the byte
  code printed by tcpdump from string to number and back.
  
  PR:		docs/123255
  Submitted by:	Eugenio Maffione, eugenio.maffione at telecomitalia.it
  MFC after:	3 days

Modified:
  head/share/man/man4/ng_bpf.4

Modified: head/share/man/man4/ng_bpf.4
==============================================================================
--- head/share/man/man4/ng_bpf.4	Fri Jan 30 18:34:54 2009	(r187934)
+++ head/share/man/man4/ng_bpf.4	Fri Jan 30 19:33:04 2009	(r187935)
@@ -156,21 +156,14 @@ INHOOK="hook1"
 MATCHHOOK="hook2"
 NOTMATCHHOOK="hook3"
 
-cat > /tmp/bpf.awk << xxENDxx
-{
-  if (!init) {
-    printf "bpf_prog_len=%d bpf_prog=[", \\$1;
-    init=1;
-  } else {
-    printf " { code=%d jt=%d jf=%d k=%d }", \\$1, \\$2, \\$3, \\$4;
-  }
-}
-END {
-  print " ]"
-}
-xxENDxx
-
-BPFPROG=`tcpdump -s 8192 -ddd ${PATTERN} | awk -f /tmp/bpf.awk`
+BPFPROG=$( tcpdump -s 8192 -ddd ${PATTERN} | \\
+           ( read len ; \\
+             echo -n "bpf_prog_len=$len" ; \\
+             echo -n "bpf_prog=[" ; \\
+             while read code jt jf k ; do \\
+                 echo -n " { code=$code jt=$jt jf=$jf k=$k }" ; \\
+             done ; \\
+             echo " ]" ) )
 
 ngctl msg ${NODEPATH} setprogram { thisHook=\\"${INHOOK}\\" \\
   ifMatch=\\"${MATCHHOOK}\\" \\