This patchset moves the masking of the upper DSCP bits in 'flowi4_tos' to the core instead of relying on callers of the FIB lookup API to do it. This will allow us to start changing users of the API to initialize the 'flowi4_tos' field with all six bits of the DSCP field. In turn, this will allow us to extend FIB rules with a new DSCP selector. By masking the upper DSCP bits in the core we are able to maintain the behavior of the TOS selector in FIB rules and routes to only match on the lower DSCP bits. While working on this I found two users of the API that do not mask the upper DSCP bits before performing the lookup. The first is an ancient netlink family that is unlikely to be used. It is adjusted in patch #1 to mask both the upper DSCP bits and the ECN bits before calling the API. The second user is a nftables module that differs in this regard from its equivalent iptables module. It is adjusted in patch #2 to invoke the API with the upper DSCP bits masked, like all other callers. The relevant selftest passed, but in the unlikely case that regressions are reported because of this change, we can restore the existing behavior using a new flow information flag as discussed here [1]. The last patch moves the masking of the upper DSCP bits to the core, making the first two patches redundant, but I wanted to post them separately to call attention to the behavior change for these two users of the FIB lookup API. Future patchsets (around 3) will start unmasking the upper DSCP bits throughout the networking stack before adding support for the new FIB rule DSCP selector. Changes from v1 [2]: Patch #3: Include <linux/ip.h> in <linux/in_route.h> instead of including it in net/ip_fib.h [1] https://lore.kernel.org/netdev/ZpqpB8vJU%2FQ6LSqa@debian/ [2] https://lore.kernel.org/netdev/20240725131729.1729103-1-idosch@xxxxxxxxxx/ Ido Schimmel (3): ipv4: Mask upper DSCP bits and ECN bits in NETLINK_FIB_LOOKUP family netfilter: nft_fib: Mask upper DSCP bits before FIB lookup ipv4: Centralize TOS matching include/net/ip_fib.h | 6 ++++++ include/uapi/linux/in_route.h | 2 ++ net/ipv4/fib_frontend.c | 2 +- net/ipv4/fib_rules.c | 2 +- net/ipv4/fib_semantics.c | 3 +-- net/ipv4/fib_trie.c | 3 +-- net/ipv4/netfilter/nft_fib_ipv4.c | 4 +--- 7 files changed, 13 insertions(+), 9 deletions(-) -- 2.46.0
