extensions: string: Adjust description of --to to recent kernel changes

This reverts commit 920ece2b392fb83bd26416e0e6f8f6a847aacbaa.

Since kernel commit c4eee56e14fe ("net: skb_find_text: Ignore patterns
extending past 'to'"), pattern scanning no longer happens past --to
offset even if skb_seq_read() returned a larger block. Point this out in
the description and also drop the '-1' offset which is not true as
kernel's selftest in tools/testing/selftests/netfilter/xt_string.sh
shows.

Closes: https://bugzilla.netfilter.org/show_bug.cgi?id=1707
Signed-off-by: Phil Sutter <phil@nwl.cc>

diff --git a/extensions/libxt_string.man b/extensions/libxt_string.man
index efdda492ae78d042e56fb5d3dc0db3b8dd794742..bdeb0a6200a88dc1a63d267bf00e24af6b21637b 100644 (file)
--- a/extensions/libxt_string.man
+++ b/extensions/libxt_string.man
@@ -7,13 +7,10 @@ Select the pattern matching strategy. (bm = Boyer-Moore, kmp = Knuth-Pratt-Morri
 Set the offset from which it starts looking for any matching. If not passed, default is 0.
 .TP
 \fB\-\-to\fP \fIoffset\fP
-Set the offset up to which should be scanned. If the pattern does not start
-within this offset, it is not considered a match.
+Set the offset up to which should be scanned. That is, byte \fIoffset\fP
+(counting from 0) is the last one that is scanned and the maximum position of
+\fIpattern\fP's last character.
 If not passed, default is the packet size.
-A second function of this parameter is instructing the kernel how much data
-from the packet should be provided. With non-linear skbuffs (e.g. due to
-fragmentation), a pattern extending past this offset may not be found. Also see
-the related note below about Boyer-Moore algorithm in these cases.
 .TP
 [\fB!\fP] \fB\-\-string\fP \fIpattern\fP
 Matches the given pattern.