On Thu, Oct 12, 2023 at 06:08:42PM +0200, Phil Sutter wrote: > 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. Then, matching on: - linear skbuff: if the pattern falls within from-to, all good. - non-linear skbuff: if pattern falls within from-to, but remaining patter This is clearly broken, the fix is just to document this? No attempt to fix it this from the kernel?
