IPPROTO_MAX used to be 256, but with the introduction of IPPROTO_MPTCP
definition, IPPROTO_MAX was bumped to 263.
IPPROTO_MPTCP definition is used for the socket interface from
userspace. It is never used in the layer 4 protocol field of
IP headers.
IPPROTO_* definitions are used anywhere in the kernel as well as in
userspace to set the layer 4 protocol field in IP headers.
At least in Netfilter, there is code in userspace that relies on
IPPROTO_MAX (not inclusive) to check for the maximum layer 4 protocol.
This patch restores IPPROTO_MAX to 256.
Fixes: faf391c3826c ("tcp: Define IPPROTO_MPTCP")
Signed-off-by: Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx>
---
Alternatively, I can also define an internal __IPPROTO_MAX to 256 in
userspace. I understand an update on uapi at this stage might be
complicated. Another possibility is to add a new definition
IPPROTO_FIELD_MAX to uapi and set it to 256 that userspace could start
using.
include/uapi/linux/in.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/include/uapi/linux/in.h b/include/uapi/linux/in.h
index 07a4cb149305..0600b03b49ee 100644
--- a/include/uapi/linux/in.h
+++ b/include/uapi/linux/in.h
@@ -80,10 +80,10 @@ enum {
IPPROTO_ETHERNET = 143, /* Ethernet-within-IPv6 Encapsulation */
#define IPPROTO_ETHERNET IPPROTO_ETHERNET
IPPROTO_RAW = 255, /* Raw IP packets */
+ IPPROTO_MAX = 256,
#define IPPROTO_RAW IPPROTO_RAW
IPPROTO_MPTCP = 262, /* Multipath TCP connection */
#define IPPROTO_MPTCP IPPROTO_MPTCP
- IPPROTO_MAX
};
#endif
--
2.30.2
