| Message ID | 165643385885.449467.3259561784742405947.stgit@firesoul (mailing list archive) |
|---|---|
| State | RFC |
| Delegated to: | BPF |
| Headers | show |
| Series | Introduce XDP-hints via BTF | expand |
Jesper Dangaard Brouer <brouer@redhat.com> writes: > XDP BPF-prog's need a way to interact with the XDP-hints. This patch > introduces a BPF-helper function, that allow XDP BPF-prog's to interact > with the XDP-hints. > > BPF-prog can query if any XDP-hints have been setup and if this is > compatible with the xdp_hints_common struct. If XDP-hints are available > the BPF "origin" is returned (see enum xdp_hints_btf_origin) as BTF can > come from different sources or origins e.g. vmlinux, module or local. I'm not sure I quite understand what this origin is supposed to be good for? What is a BPF (or AF_XDP) program supposed to do with the information "this XDP hints struct came from a module?" without knowing which module that was? Ultimately, the origin is useful for a consumer to check that the metadata is in the format that it's expecting it to be in (so it can just load the data from the appropriate offsets). But to answer this, we really need a unique identifier; so I think the approach in Alexander's series of encoding the ID of the BTF structure itself into the next 32 bits is better? That way we'll have a unique "pointer" to the actual struct that's in the metadata area and can act on this. > RFC/TODO: Improve patch: Can verifier validate provided BTF on "update" > and detect if compatible with common struct??? If we have the unique ID as mentioned above, I think the kernel probably could resolve this automatically: whenever a module is loaded, the kernel could walk the BTF information from that module an simply inspect all the metadata structs and see if they contain the embedded xdp_hints_common struct. The IDs of any metadata structs that do contain the common struct can then be kept in a central lookup table and the consumption code can then simply compare the BTF ID to this table when building an SKB? As for the validation on the BPF side:n > + if (flags & HINTS_BTF_UPDATE) { > + is_compat_common = !!(flags & HINTS_BTF_COMPAT_COMMON); > + /* TODO: Can kernel validate if hints are BTF compat with common? */ > + /* TODO: Could BPF prog provide BTF as ARG_PTR_TO_BTF_ID to prove compat_common ? */ If we use the "global ID + lookup table" approach above, we don't really need to validate anything here: if the program says it's writing metadata with a format given by a specific ID, that implies compatibility (or not) as given by the ID. We could sanity-check the metadata area size, but the consumption code has to do that anyway, so I'm not sure it's worth the runtime overhead to have an additional check here? As for safety of the metadata content itself, I don't really think we can do anything to guarantee this: in any case the BPF program can pass a valid BTF ID and still write garbage values into the actual fields, so the consumption code has to do enough validation that this won't crash the kernel anyway. But this is no different from the packet data itself: XDP is basically in a position to be a MITM attacker of the network stack itself, which is why loading XDP programs is a privileged operation... -Toke
On 29/06/2022 16.20, Toke Høiland-Jørgensen wrote: > Jesper Dangaard Brouer <brouer@redhat.com> writes: > >> XDP BPF-prog's need a way to interact with the XDP-hints. This patch >> introduces a BPF-helper function, that allow XDP BPF-prog's to interact >> with the XDP-hints. >> >> BPF-prog can query if any XDP-hints have been setup and if this is >> compatible with the xdp_hints_common struct. If XDP-hints are available >> the BPF "origin" is returned (see enum xdp_hints_btf_origin) as BTF can >> come from different sources or origins e.g. vmlinux, module or local. > > I'm not sure I quite understand what this origin is supposed to be good > for? Some background info on BTF is needed here: BTF_ID numbers are not globally unique identifiers, thus we need to know where it originate from, to make it unique (as we store this BTF_ID in XDP-hints). There is a connection between origin "vmlinux" and "module", which is that vmlinux will start at ID=1 and end at a max ID number. Modules refer to ID's in "vmlinux", and for this to work, they will shift their own numbering to start after ID=max-vmlinux-id. Origin "local" is for BTF information stored in the BPF-ELF object file. Their numbering starts at ID=1. The use-case is that a BPF-prog want to extend the kernel drivers BTF-layout, and e.g. add a RX-timestamp like [1]. Then BPF-prog can check if it knows module's BTF_ID and then extend via bpf_xdp_adjust_meta, and update BTF_ID in XDP-hints and call the helper (I introduced) marking this as origin "local" for kernel to know this is no-longer origin "module". [1] https://github.com/xdp-project/bpf-examples/tree/master/AF_XDP-interaction/ > What is a BPF (or AF_XDP) program supposed to do with the > information "this XDP hints struct came from a module?" without knowing > which module that was? For AF_XDP my claim is the userspace program will already know that driver it is are talking to because it need to "bind" to a specific interface (and attach to XDP-prog to ifindex). See sample code[2] for get_driver_name from ifindex. Thus, part of using XDP-hints already involves (resolving and) opening /sys/kernel/btf/driver_name. So the origin "module" is enough for the API end-user to make the BTF_ID unique. Runtime the BPF-prog and kernel can find out what net_device the origin "module" refers to via xdp_buff->rxq->dev. When an end-user/program attach XDP they also need to know the ifindex, again giving them knowledge that make origin "module" BTF_ID's unique for them, Same way the origin "local" have meaning to the BPF-prog and user loading it. [2] https://github.com/torvalds/linux/blob/v5.18/samples/bpf/xdp_sample_user.c#L1602 > Ultimately, the origin is useful for a consumer > to check that the metadata is in the format that it's expecting it to be > in (so it can just load the data from the appropriate offsets). But to > answer this, we really need a unique identifier; so I think the approach > in Alexander's series of encoding the ID of the BTF structure itself > into the next 32 bits is better? That way we'll have a unique "pointer" > to the actual struct that's in the metadata area and can act on this. I would really like an explanation from Alexander, how his approach creates unique identifier across all kernel modules. I don't get it from reading the code. To me it looks like some extra BTF "type" information about the BTF_ID. E.g. how do BTF "local" BPF-ELF object's get a unique identifier, that doesn't overlap with e.g. kernel modules? >> RFC/TODO: Improve patch: Can verifier validate provided BTF on "update" >> and detect if compatible with common struct??? > > If we have the unique ID as mentioned above, I think the kernel probably > could resolve this automatically: whenever a module is loaded, the > kernel could walk the BTF information from that module an simply inspect > all the metadata structs and see if they contain the embedded > xdp_hints_common struct. The IDs of any metadata structs that do contain > the common struct can then be kept in a central lookup table and the > consumption code can then simply compare the BTF ID to this table when > building an SKB? I'm not against the idea for the kernel to keep track of these structs. I just don't like the idea of checking this runtime, especially as this approach for walking all other modules BTF struct's doesn't scale. > As for the validation on the BPF side:n > >> + if (flags & HINTS_BTF_UPDATE) { >> + is_compat_common = !!(flags & HINTS_BTF_COMPAT_COMMON); >> + /* TODO: Can kernel validate if hints are BTF compat with common? */ >> + /* TODO: Could BPF prog provide BTF as ARG_PTR_TO_BTF_ID to prove compat_common ? */ > > If we use the "global ID + lookup table" approach above, we don't really > need to validate anything here: if the program says it's writing > metadata with a format given by a specific ID, that implies > compatibility (or not) as given by the ID. We could sanity-check the > metadata area size, but the consumption code has to do that anyway, so > I'm not sure it's worth the runtime overhead to have an additional check > here? As you know I hate "runtime checks", and try hard to push checks to "setup time". Maybe we could have verifier (or libbpf) do the check at setup/load time, by identifying the helper call and check if provided BTF do match COMPAT_COMMON claim. For this to work, the verifier need to be able to resolve origin "module", which happens at BPF load-time, so we would need to set the ifindex (curr used for XDP-hardware-offload) at BPF load-time. > As for safety of the metadata content itself, I don't really think we > can do anything to guarantee this: in any case the BPF program can pass > a valid BTF ID and still write garbage values into the actual fields, so > the consumption code has to do enough validation that this won't crash > the kernel anyway. But this is no different from the packet data itself: > XDP is basically in a position to be a MITM attacker of the network > stack itself, which is why loading XDP programs is a privileged > operation... I agree, that we cannot stop the end-user from screwing up their BPF-prog to provide garbage in the fields, as long as it doesn't crash the kernel. I do think it would improve usability for end-users if we can detect and report that their BPF-prog have gotten out of sync with the running kernel and their claim that their BTF layout are COMPAT_COMMON isn't actually true. But I guess it is shouldn't block the code, as it's only an extra usability help. --Jesper
Jesper Dangaard Brouer <jbrouer@redhat.com> writes: > On 29/06/2022 16.20, Toke Høiland-Jørgensen wrote: >> Jesper Dangaard Brouer <brouer@redhat.com> writes: >> >>> XDP BPF-prog's need a way to interact with the XDP-hints. This patch >>> introduces a BPF-helper function, that allow XDP BPF-prog's to interact >>> with the XDP-hints. >>> >>> BPF-prog can query if any XDP-hints have been setup and if this is >>> compatible with the xdp_hints_common struct. If XDP-hints are available >>> the BPF "origin" is returned (see enum xdp_hints_btf_origin) as BTF can >>> come from different sources or origins e.g. vmlinux, module or local. >> >> I'm not sure I quite understand what this origin is supposed to be good >> for? > > Some background info on BTF is needed here: BTF_ID numbers are not > globally unique identifiers, thus we need to know where it originate > from, to make it unique (as we store this BTF_ID in XDP-hints). > > There is a connection between origin "vmlinux" and "module", which is > that vmlinux will start at ID=1 and end at a max ID number. Modules > refer to ID's in "vmlinux", and for this to work, they will shift their > own numbering to start after ID=max-vmlinux-id. > > Origin "local" is for BTF information stored in the BPF-ELF object file. > Their numbering starts at ID=1. The use-case is that a BPF-prog want to > extend the kernel drivers BTF-layout, and e.g. add a RX-timestamp like > [1]. Then BPF-prog can check if it knows module's BTF_ID and then > extend via bpf_xdp_adjust_meta, and update BTF_ID in XDP-hints and call > the helper (I introduced) marking this as origin "local" for kernel to > know this is no-longer origin "module". Right, I realise that :) My point was that just knowing "this is a BTF ID coming from a module" is not terribly useful; you could already figure that out by just looking at the ID and seeing if it's larger than the maximum ID in vmlinux BTF. Rather, what we need is a way to identify *which* module the BTF ID comes from; and luckily, the kernel assigns a unique ID to every BTF *object* as well as to each type ID within that object. These can be dumped by bpftool: # bpftool btf bpftool btf [sudo] password for alrua: 1: name [vmlinux] size 4800187B 2: name [serio] size 2588B 3: name [i8042] size 11786B 4: name [rng_core] size 8184B [...] 2062: name <anon> size 36965B pids bpftool(547298) IDs 2-4 are module BTF objects, and that last one is the ID of a BTF object loaded along with a BPF program by bpftool itself... So we *do* in fact have a unique ID, by combining the BTF object ID with the type ID; this is what Alexander is proposing to put into the xdp-hints struct as well (combining the two IDs into a single u64). >> What is a BPF (or AF_XDP) program supposed to do with the >> information "this XDP hints struct came from a module?" without knowing >> which module that was? > > For AF_XDP my claim is the userspace program will already know that > driver it is are talking to because it need to "bind" to a specific > interface (and attach to XDP-prog to ifindex). See sample code[2] for > get_driver_name from ifindex. > Thus, part of using XDP-hints already involves (resolving and) opening > /sys/kernel/btf/driver_name. So the origin "module" is enough for the > API end-user to make the BTF_ID unique. This will probably work in the most common cases, but offers no way to verify that this "offline" resolution of module ID is actually correct. Explicitly encoding the full unique ID will be more robust. > Runtime the BPF-prog and kernel can find out what net_device the origin > "module" refers to via xdp_buff->rxq->dev. When an end-user/program > attach XDP they also need to know the ifindex, again giving them > knowledge that make origin "module" BTF_ID's unique for them, Right, but then the BPF program needs to keep its own lookup table from ifindex to BTF ID? If we just encode the full ID in the packet, it's a simple check, and we can likely create a "magic" CO-RE macro that turns a struct definition into the right ID check at load time... >> Ultimately, the origin is useful for a consumer >> to check that the metadata is in the format that it's expecting it to be >> in (so it can just load the data from the appropriate offsets). But to >> answer this, we really need a unique identifier; so I think the approach >> in Alexander's series of encoding the ID of the BTF structure itself >> into the next 32 bits is better? That way we'll have a unique "pointer" >> to the actual struct that's in the metadata area and can act on this. > > I would really like an explanation from Alexander, how his approach > creates unique identifier across all kernel modules. I don't get it > from reading the code. To me it looks like some extra BTF "type" > information about the BTF_ID. > > E.g. how do BTF "local" BPF-ELF object's get a unique identifier, that > doesn't overlap with e.g. kernel modules? See above: the kernel generates a unique (until the next reboot) ID for every BTF object when it's loaded into the kernel. >>> RFC/TODO: Improve patch: Can verifier validate provided BTF on "update" >>> and detect if compatible with common struct??? >> >> If we have the unique ID as mentioned above, I think the kernel probably >> could resolve this automatically: whenever a module is loaded, the >> kernel could walk the BTF information from that module an simply inspect >> all the metadata structs and see if they contain the embedded >> xdp_hints_common struct. The IDs of any metadata structs that do contain >> the common struct can then be kept in a central lookup table and the >> consumption code can then simply compare the BTF ID to this table when >> building an SKB? > > I'm not against the idea for the kernel to keep track of these structs. > I just don't like the idea of checking this runtime, especially as this > approach for walking all other modules BTF struct's doesn't scale. Yeah, we should optimise this. See below... >> As for the validation on the BPF side:n >> >>> + if (flags & HINTS_BTF_UPDATE) { >>> + is_compat_common = !!(flags & HINTS_BTF_COMPAT_COMMON); >>> + /* TODO: Can kernel validate if hints are BTF compat with common? */ >>> + /* TODO: Could BPF prog provide BTF as ARG_PTR_TO_BTF_ID to prove compat_common ? */ >> >> If we use the "global ID + lookup table" approach above, we don't really >> need to validate anything here: if the program says it's writing >> metadata with a format given by a specific ID, that implies >> compatibility (or not) as given by the ID. We could sanity-check the >> metadata area size, but the consumption code has to do that anyway, so >> I'm not sure it's worth the runtime overhead to have an additional check >> here? > > As you know I hate "runtime checks", and try hard to push checks to > "setup time". Maybe we could have verifier (or libbpf) do the check at > setup/load time, by identifying the helper call and check if provided > BTF do match COMPAT_COMMON claim. > > For this to work, the verifier need to be able to resolve origin > "module", which happens at BPF load-time, so we would need to set the > ifindex (curr used for XDP-hardware-offload) at BPF load-time. If we make the UAPI on the BPF side just accept a full BTF object+type ID, and also require that the value being passed to the helper is a compile-time constant (so it is visible to the verifier at verification time), it is straight-forward for the verifier to just lookup the BTF type, check if it contains the "hints_common" struct and if it does, rewrite the helper call to set the right value of the "compat_common" flag without exposing the flag itself as UAPI. The driver code would probably still have to set this flag "manually", but that's internal kernel API, so that's probably fine... >> As for safety of the metadata content itself, I don't really think we >> can do anything to guarantee this: in any case the BPF program can pass >> a valid BTF ID and still write garbage values into the actual fields, so >> the consumption code has to do enough validation that this won't crash >> the kernel anyway. But this is no different from the packet data itself: >> XDP is basically in a position to be a MITM attacker of the network >> stack itself, which is why loading XDP programs is a privileged >> operation... > > I agree, that we cannot stop the end-user from screwing up their > BPF-prog to provide garbage in the fields, as long as it doesn't crash > the kernel. I do think it would improve usability for end-users if we > can detect and report that their BPF-prog have gotten out of sync with > the running kernel and their claim that their BTF layout are > COMPAT_COMMON isn't actually true. But I guess it is shouldn't block > the code, as it's only an extra usability help. Yeah, I agree this could be error prone; which is why I think not exposing the flag itself as UAPI is a better solution ;) -Toke
diff --git a/include/net/xdp.h b/include/net/xdp.h index 5b77fc8fe5ce..710d145a26f9 100644 --- a/include/net/xdp.h +++ b/include/net/xdp.h @@ -199,14 +199,22 @@ struct xdp_txq_info { }; enum xdp_buff_flags { - XDP_FLAGS_HAS_FRAGS = BIT(0), /* non-linear xdp buff */ - XDP_FLAGS_FRAGS_PF_MEMALLOC = BIT(1), /* xdp paged memory is under + XDP_FLAGS_HINTS_ORIGIN_BIT0 = BIT(0),/* enum xdp_hints_btf_origin */ + XDP_FLAGS_HINTS_ORIGIN_BIT1 = BIT(1), +#define XDP_FLAGS_HINTS_COMPAT_COMMON_ BIT(3) /* HINTS_BTF_COMPAT_COMMON */ + XDP_FLAGS_HINTS_COMPAT_COMMON = XDP_FLAGS_HINTS_COMPAT_COMMON_, + + XDP_FLAGS_HAS_FRAGS = BIT(4), /* non-linear xdp buff */ + XDP_FLAGS_FRAGS_PF_MEMALLOC = BIT(5), /* xdp paged memory is under * pressure */ - XDP_FLAGS_HAS_HINTS = BIT(2), - XDP_FLAGS_HINTS_COMPAT_COMMON = BIT(3), }; +#define XDP_FLAGS_HINTS_ORIGIN_MASK (XDP_FLAGS_HINTS_ORIGIN_BIT0 | \ + XDP_FLAGS_HINTS_ORIGIN_BIT1) +#define XDP_FLAGS_HINTS_RETURN_MASK (XDP_FLAGS_HINTS_ORIGIN_MASK | \ + XDP_FLAGS_HINTS_COMPAT_COMMON) + struct xdp_buff { void *data; void *data_end; @@ -243,6 +251,32 @@ static __always_inline void xdp_buff_set_frag_pfmemalloc(struct xdp_buff *xdp) xdp->flags |= XDP_FLAGS_FRAGS_PF_MEMALLOC; } +static __always_inline bool xdp_buff_has_hints(struct xdp_buff *xdp) +{ + return !!(xdp->flags & XDP_FLAGS_HINTS_ORIGIN_MASK); +} + +static __always_inline bool xdp_buff_has_hints_compat(struct xdp_buff *xdp) +{ + u32 flags = xdp->flags; + + if (!(flags & XDP_FLAGS_HINTS_COMPAT_COMMON)) + return false; + + return !!(flags & XDP_FLAGS_HINTS_ORIGIN_MASK); +} + +static __always_inline void xdp_buff_set_hints(struct xdp_buff *xdp, + u32 btf_origin, + bool is_compat_common) +{ + u32 common = is_compat_common ? XDP_FLAGS_HINTS_COMPAT_COMMON : 0; + + /* enum xdp_hints_btf_origin */ + btf_origin &= XDP_FLAGS_HINTS_ORIGIN_MASK; + xdp->flags |= btf_origin | common; +} + static __always_inline void xdp_init_buff(struct xdp_buff *xdp, u32 frame_sz, struct xdp_rxq_info *rxq) { diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h index e81362891596..1c3780c02239 100644 --- a/include/uapi/linux/bpf.h +++ b/include/uapi/linux/bpf.h @@ -5325,6 +5325,31 @@ union bpf_attr { * **-EACCES** if the SYN cookie is not valid. * * **-EPROTONOSUPPORT** if CONFIG_IPV6 is not builtin. + * + * long xdp_hints_btf(struct xdp_buff *xdp_md, u32 btf_origin, u64 flags) + * Description + * Update and get info on XDP hints BTF type and origin. + * + * Drivers can provide XDP-hints information via the metadata area, + * which defines the layout of this area via BTF. The BTF ID is + * available as the last member. The BTF ID can originate from + * different sources, e.g. vmlinux, module or local BTF-object. + * + * In-case a BPF-prog want to redefine the layout of this area it + * should update the BTF ID (last-member) and MUST call this helper + * to specify the origin for the BTF ID. + * + * If updating the BTF ID then caller can request that the layout + * is compatible with kernels xdp_hints_common. This is then + * validated (TODO HOW?!?) before kernel side trust this can be + * used for e.g. populating SKB fields. + * + * The **flags** are used to control the mode of the helper. + * + * Return + * Returns indications on whether XDP-hints were populated by + * driver via an 'origin' value and whether this layout is + * compatible with kernels xdp_hints_common. */ #define __BPF_FUNC_MAPPER(FN) \ FN(unspec), \ @@ -5535,6 +5560,7 @@ union bpf_attr { FN(tcp_raw_gen_syncookie_ipv6), \ FN(tcp_raw_check_syncookie_ipv4), \ FN(tcp_raw_check_syncookie_ipv6), \ + FN(xdp_hints_btf), \ /* */ /* integer value in 'imm' field of BPF_CALL instruction selects which helper @@ -5946,6 +5972,23 @@ struct xdp_md { __u32 egress_ifindex; /* txq->dev->ifindex */ }; +/* Mode flags for BPF_FUNC_xdp_hints_btf helper. */ +enum xdp_hints_btf_mode_flags { + HINTS_BTF_QUERY_ONLY = (1U << 0), + HINTS_BTF_UPDATE = (1U << 1), + HINTS_BTF_DISABLE = (1U << 2), + HINTS_BTF_COMPAT_COMMON = (1U << 3), +}; + +/* BTF can come from different sources e.g. vmlinux, module or local */ +enum xdp_hints_btf_origin { + BTF_ORIGIN_NONE = 0, + BTF_ORIGIN_VMLINUX = 1, + BTF_ORIGIN_MODULE = 2, + BTF_ORIGIN_LOCAL = 3, + BTF_ORIGIN_MASK = 0x3, +}; + /* DEVMAP map-value layout * * The struct data-layout of map-value is a configuration interface. diff --git a/net/core/filter.c b/net/core/filter.c index 151aa4756bd6..614054f89fdc 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -6129,6 +6129,49 @@ static const struct bpf_func_proto bpf_xdp_check_mtu_proto = { .arg5_type = ARG_ANYTHING, }; +/* btf_origin type &enum xdp_hints_btf_origin + * flags type &enum xdp_hints_btf_mode_flags + */ +BPF_CALL_3(bpf_xdp_hints_btf, struct xdp_buff *, xdp, u32, btf_origin, u64, flags) +{ + s64 ret = BTF_ORIGIN_NONE; + bool is_compat_common; + + if (flags & HINTS_BTF_QUERY_ONLY) { + BUILD_BUG_ON(HINTS_BTF_COMPAT_COMMON != XDP_FLAGS_HINTS_COMPAT_COMMON_); + ret = xdp->flags & XDP_FLAGS_HINTS_RETURN_MASK; + goto out; + } + if (flags & HINTS_BTF_DISABLE) { + xdp_buff_set_hints(xdp, BTF_ORIGIN_NONE, false); + goto out; + } + if (flags & HINTS_BTF_UPDATE) { + is_compat_common = !!(flags & HINTS_BTF_COMPAT_COMMON); + /* TODO: Can kernel validate if hints are BTF compat with common? */ + /* TODO: Could BPF prog provide BTF as ARG_PTR_TO_BTF_ID to prove compat_common ? */ + /* TODO: Validate if metadata size is >= sizeof(xdp_hints_common) */ + btf_origin &= BTF_ORIGIN_MASK; + /* TODO: Validate if module BTF_ID is large than vmlinux base */ + xdp_buff_set_hints(xdp, btf_origin, is_compat_common); + BUILD_BUG_ON(BTF_ORIGIN_MASK != XDP_FLAGS_HINTS_ORIGIN_MASK); + ret = xdp->flags & XDP_FLAGS_HINTS_RETURN_MASK; + goto out; + } + + out: + return ret; +} + +static const struct bpf_func_proto bpf_xdp_hints_btf_proto = { + .func = bpf_xdp_hints_btf, + .gpl_only = true, + .ret_type = RET_INTEGER, + .arg1_type = ARG_PTR_TO_CTX, + .arg2_type = ARG_ANYTHING, + .arg3_type = ARG_ANYTHING, +}; + #if IS_ENABLED(CONFIG_IPV6_SEG6_BPF) static int bpf_push_seg6_encap(struct sk_buff *skb, u32 type, void *hdr, u32 len) { @@ -7959,6 +8002,8 @@ xdp_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog) return &bpf_xdp_fib_lookup_proto; case BPF_FUNC_check_mtu: return &bpf_xdp_check_mtu_proto; + case BPF_FUNC_xdp_hints_btf: + return &bpf_xdp_hints_btf_proto; #ifdef CONFIG_INET case BPF_FUNC_sk_lookup_udp: return &bpf_xdp_sk_lookup_udp_proto;
XDP BPF-prog's need a way to interact with the XDP-hints. This patch introduces a BPF-helper function, that allow XDP BPF-prog's to interact with the XDP-hints. BPF-prog can query if any XDP-hints have been setup and if this is compatible with the xdp_hints_common struct. If XDP-hints are available the BPF "origin" is returned (see enum xdp_hints_btf_origin) as BTF can come from different sources or origins e.g. vmlinux, module or local. Remember that XDP-hints are setup by the driver prior to calling the XDP BPF-prog, which is useful for adjusting the HW provided XDP-hints in-case of HW issues or missing HW features, for use-case like xdp2skb or AF_XDP. The BPP-prog might also prefer to use metadata area for other things, either disabling XDP-hints or updating with another XDP-hints layout that might still be compatible with common struct. Thus, helper have "update" and "delete" mode flags. RFC/TODO: Improve patch: Can verifier validate provided BTF on "update" and detect if compatible with common struct??? Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com> --- include/net/xdp.h | 42 ++++++++++++++++++++++++++++++++++++++---- include/uapi/linux/bpf.h | 43 +++++++++++++++++++++++++++++++++++++++++++ net/core/filter.c | 45 +++++++++++++++++++++++++++++++++++++++++++++ 3 files changed, 126 insertions(+), 4 deletions(-)