| Message ID | 1447160049-29214-1-git-send-email-phil@nwl.cc |
|---|---|
| State | Rejected, archived |
| Delegated to: | stephen hemminger |
| Headers | show |
On Tue, 10 Nov 2015 13:54:09 +0100 Phil Sutter <phil@nwl.cc> wrote: > Technically, the range of possible hoplimit values are defined by IPv4 > and IPv6 header formats. Both define the field to be eight bits in size, > which leads to a value range of [0;255]. Setting a packet's hoplimit > field to 0 though makes not much sense, as the next hop would > immediately drop the packet. Therefore Linux uses 0 as a special value > indicating to use the system's default hoplimit (configurable via > sysctl). In iproute, setting the hoplimit of a route to 0 is equivalent > to omitting the hoplimit parameter alltogether, so it is not necessary > to allow that value to be specified. > > Signed-off-by: Phil Sutter <phil@nwl.cc> Even though it doesn't make much sense to set hoplimit of 0; I am concerned that some user is doing that now, and changing this would break a working (but not optimum or sane) configuration. Especially if actual config is auto-generated. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/ip/iproute.c b/ip/iproute.c index c0ef7bf..e0c8e4c 100644 --- a/ip/iproute.c +++ b/ip/iproute.c @@ -931,7 +931,8 @@ static int iproute_modify(int cmd, unsigned flags, int argc, char **argv) mxlock |= (1<<RTAX_HOPLIMIT); NEXT_ARG(); } - if (get_unsigned(&hoplimit, *argv, 0)) + if (get_unsigned(&hoplimit, *argv, 0) || + hoplimit < 1 || hoplimit > 255) invarg("\"hoplimit\" value is invalid\n", *argv); rta_addattr32(mxrta, sizeof(mxbuf), RTAX_HOPLIMIT, hoplimit); } else if (strcmp(*argv, "advmss") == 0) {
Technically, the range of possible hoplimit values are defined by IPv4 and IPv6 header formats. Both define the field to be eight bits in size, which leads to a value range of [0;255]. Setting a packet's hoplimit field to 0 though makes not much sense, as the next hop would immediately drop the packet. Therefore Linux uses 0 as a special value indicating to use the system's default hoplimit (configurable via sysctl). In iproute, setting the hoplimit of a route to 0 is equivalent to omitting the hoplimit parameter alltogether, so it is not necessary to allow that value to be specified. Signed-off-by: Phil Sutter <phil@nwl.cc> --- ip/iproute.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)