[iptables PATCH] extensions: string: Clarify description of --to

[Phil Sutter <phil@nwl.cc>]

String match indeed returns a match as long as the given pattern starts
in the range of --from and --to, update the text accordingly.
Also add a note regarding fragment boundaries.

Closes: https://bugzilla.netfilter.org/show_bug.cgi?id=1707
Signed-off-by: Phil Sutter <phil@nwl.cc>
---
 extensions/libxt_string.man | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/extensions/libxt_string.man b/extensions/libxt_string.man
index 2a470ece19c9d..efdda492ae78d 100644
--- a/extensions/libxt_string.man
+++ b/extensions/libxt_string.man
@@ -7,9 +7,13 @@ 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. That is, byte \fIoffset\fP-1
-(counting from 0) is the last one that is scanned.
+Set the offset up to which should be scanned. If the pattern does not start
+within this offset, it is not considered a match.
 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.
-- 
2.41.0