| Message ID | 20201130183705.17540-1-toke@redhat.com |
|---|---|
| State | New |
| Headers | show |
| Series | [net] inet_ecn: Fix endianness of checksum update when setting ECT(1) | expand |
On Mon, 30 Nov 2020 19:37:05 +0100 Toke Høiland-Jørgensen wrote: > When adding support for propagating ECT(1) marking in IP headers it seems I > suffered from endianness-confusion in the checksum update calculation: In > fact the ECN field is in the *lower* bits of the first 16-bit word of the > IP header when calculating in network byte order. This means that the > addition performed to update the checksum field was wrong; let's fix that. > > Fixes: b723748750ec ("tunnel: Propagate ECT(1) when decapsulating as recommended by RFC6040") > Reported-by: Jonathan Morton <chromatix99@gmail.com> > Tested-by: Pete Heist <pete@heistp.net> > Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com> Applied and queued, thanks! > diff --git a/include/net/inet_ecn.h b/include/net/inet_ecn.h > index e1eaf1780288..563457fec557 100644 > --- a/include/net/inet_ecn.h > +++ b/include/net/inet_ecn.h > @@ -107,7 +107,7 @@ static inline int IP_ECN_set_ect1(struct iphdr *iph) > if ((iph->tos & INET_ECN_MASK) != INET_ECN_ECT_0) > return 0; > > - check += (__force u16)htons(0x100); > + check += (__force u16)htons(0x1); > > iph->check = (__force __sum16)(check + (check>=0xFFFF)); > iph->tos ^= INET_ECN_MASK; This seems to be open coding csum16_add() - is there a reason and if not perhaps worth following up in net-next?
Jakub Kicinski <kuba@kernel.org> writes: > On Mon, 30 Nov 2020 19:37:05 +0100 Toke Høiland-Jørgensen wrote: >> When adding support for propagating ECT(1) marking in IP headers it seems I >> suffered from endianness-confusion in the checksum update calculation: In >> fact the ECN field is in the *lower* bits of the first 16-bit word of the >> IP header when calculating in network byte order. This means that the >> addition performed to update the checksum field was wrong; let's fix that. >> >> Fixes: b723748750ec ("tunnel: Propagate ECT(1) when decapsulating as recommended by RFC6040") >> Reported-by: Jonathan Morton <chromatix99@gmail.com> >> Tested-by: Pete Heist <pete@heistp.net> >> Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com> > > Applied and queued, thanks! > >> diff --git a/include/net/inet_ecn.h b/include/net/inet_ecn.h >> index e1eaf1780288..563457fec557 100644 >> --- a/include/net/inet_ecn.h >> +++ b/include/net/inet_ecn.h >> @@ -107,7 +107,7 @@ static inline int IP_ECN_set_ect1(struct iphdr *iph) >> if ((iph->tos & INET_ECN_MASK) != INET_ECN_ECT_0) >> return 0; >> >> - check += (__force u16)htons(0x100); >> + check += (__force u16)htons(0x1); >> >> iph->check = (__force __sum16)(check + (check>=0xFFFF)); >> iph->tos ^= INET_ECN_MASK; > > This seems to be open coding csum16_add() - is there a reason and if > not perhaps worth following up in net-next? Hmm, good point. I think I originally just copied this from IP_ECN_set_ce(), which comes all the way back from the initial Linux-2.6.12-rc2 commit in git. So I suppose it may just predate the csum helpers? I'll wait for this patch to get propagated to net-next, then follow up with a fix there :) -Toke
diff --git a/include/net/inet_ecn.h b/include/net/inet_ecn.h index e1eaf1780288..563457fec557 100644 --- a/include/net/inet_ecn.h +++ b/include/net/inet_ecn.h @@ -107,7 +107,7 @@ static inline int IP_ECN_set_ect1(struct iphdr *iph) if ((iph->tos & INET_ECN_MASK) != INET_ECN_ECT_0) return 0; - check += (__force u16)htons(0x100); + check += (__force u16)htons(0x1); iph->check = (__force __sum16)(check + (check>=0xFFFF)); iph->tos ^= INET_ECN_MASK;
When adding support for propagating ECT(1) marking in IP headers it seems I suffered from endianness-confusion in the checksum update calculation: In fact the ECN field is in the *lower* bits of the first 16-bit word of the IP header when calculating in network byte order. This means that the addition performed to update the checksum field was wrong; let's fix that. Fixes: b723748750ec ("tunnel: Propagate ECT(1) when decapsulating as recommended by RFC6040") Reported-by: Jonathan Morton <chromatix99@gmail.com> Tested-by: Pete Heist <pete@heistp.net> Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com> --- include/net/inet_ecn.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)