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@xxxxxx> --- 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
