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AF_XDP-interaction: introduce struct to mirror kernel-side struct

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The 'struct xdp_hints_rx_time' exist both in kernel-side (af_xdp_kern.c)
and userspace program af_xdp_user.c, but are very different.

The kernel-side is the actual XDP-hints memory layout used in metadata area.

The userspace side uses the same struct name, but contains BTF info
that allow us to access the struct members from kernel-side struct.
The BTF info is extracted on userspace startup, from the BPF-prog
ELF data BTF section.

Caching BTF lookups at startup is done, as target application
is a real-time application.

Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
This commit is contained in:
Jesper Dangaard Brouer
2021-11-09 16:50:35 +01:00
parent 5e93cf0993
commit 1cb72f03df
2 changed files with 50 additions and 27 deletions
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76
AF_XDP-interaction/af_xdp_user.c
View File

@@ -327,14 +327,18 @@ struct xdp_hints {
const char *struct_name;
};
static struct xdp_hints xdp_meta_with_time = {
.struct_name = "xdp_hints_rx_time",
};
static struct xdp_hints xdp_meta_with_mark = {
.struct_name = "xdp_hints_mark",
};
/* This struct BTF mirrors kernel-side struct xdp_hints_rx_time
*/
struct xdp_hints_rx_time {
__u32 btf_type_id; /* cached xsk_btf__btf_type_id(xbi) */
struct xsk_btf_info *xbi;
struct xsk_btf_member rx_ktime;
} xdp_hints_rx_time;
int init_xdp_hints(struct btf *btf_obj, struct xdp_hints *xh)
{
int err;
@@ -354,30 +358,53 @@ int init_xdp_hints(struct btf *btf_obj, struct xdp_hints *xh)
return 0;
}
static struct xsk_btf_member member_rx_ktime;
struct xsk_btf_info *setup_btf_info(struct btf *btf,
const char *struct_name)
{
struct xsk_btf_info *xbi = NULL;
int err;
err = xsk_btf__init_xdp_hint(btf, struct_name, &xbi);
if (err) {
fprintf(stderr, "ERR(%d): Cannot BTF find struct:%s\n",
err, struct_name);
return NULL;
}
if (!xsk_btf__has_field("btf_id", xbi)) {
fprintf(stderr, "ERR: %s doesn't contain member btf_id\n",
struct_name);
xsk_btf__free_xdp_hint(xbi);
return NULL;
}
if (debug_meta)
printf("Setup BTF based XDP hints for struct: %s\n",
struct_name);
return xbi;
}
int init_btf_info_via_bpf_object(struct bpf_object *bpf_obj)
{
struct btf *btf = bpf_object__btf(bpf_obj);
struct xsk_btf_info *xbi = NULL;
int err;
if ((err = init_xdp_hints(btf, &xdp_meta_with_time)))
return err;
xbi = setup_btf_info(btf, "xdp_hints_rx_time");
xdp_hints_rx_time.btf_type_id = 0;
if (xbi) {
/* Lookup info on member "rx_ktime" */
if (!xsk_btf__field_member("rx_ktime", xbi,
&xdp_hints_rx_time.rx_ktime))
return -EBADSLT;
xdp_hints_rx_time.btf_type_id = xsk_btf__btf_type_id(xbi);
xdp_hints_rx_time.xbi = xbi;
}
if ((err = init_xdp_hints(btf, &xdp_meta_with_mark)))
return err;
/* Check member with "rx_ktime" exist */
if (!xsk_btf__has_field("rx_ktime", xdp_meta_with_time.xbi)) {
return -EBADSLT;
}
/* Cache member "rx_ktime" */
if (!xsk_btf__field_member("rx_ktime", xdp_meta_with_time.xbi,
&member_rx_ktime)) {
return -EBADSLT;
}
/* Check member with "mark" exist */
if (!xsk_btf__has_field("mark", xdp_meta_with_mark.xbi)) {
return -EBADSLT;
@@ -398,7 +425,7 @@ static void print_meta_info_mark(uint8_t *pkt)
static int print_meta_info_time(uint8_t *pkt)
{
struct xsk_btf_info *xbi = xdp_meta_with_time.xbi;
struct xsk_btf_info *xbi = xdp_hints_rx_time.xbi;
__u64 time_now; // = gettime();
__u64 *rx_ktime_ptr; /* Points directly to member memory */
__u64 rx_ktime;
@@ -425,9 +452,8 @@ static int print_meta_info_time(uint8_t *pkt)
return 0;
}
static int print_meta_info_time_faster(uint8_t *pkt)
static int print_meta_info_time_faster(uint8_t *pkt, struct xdp_hints_rx_time *meta)
{
struct xsk_btf_info *xbi = xdp_meta_with_time.xbi;
__u64 time_now; // = gettime();
__u64 *rx_ktime_ptr; /* Points directly to member memory */
__u64 rx_ktime;
@@ -436,7 +462,7 @@ static int print_meta_info_time_faster(uint8_t *pkt)
/* Use API that doesn't involve allocations to access BTF struct member */
err = xsk_btf__read_member((void **)&rx_ktime_ptr, sizeof(*rx_ktime_ptr),
&member_rx_ktime, xbi, pkt);
&meta->rx_ktime, meta->xbi, pkt);
if (err) {
fprintf(stderr, "ERROR(%d) no rx_ktime?!\n", err);
return err;
@@ -457,12 +483,10 @@ static void print_meta_info_via_btf( uint8_t *pkt)
{
__u32 btf_id = xsk_umem__btf_id(pkt);
__u32 meta_time = xsk_btf__btf_type_id(xdp_meta_with_time.xbi);
__u32 meta_mark = xsk_btf__btf_type_id(xdp_meta_with_mark.xbi);
if (btf_id == meta_time) {
//print_meta_info_time(pkt);
print_meta_info_time_faster(pkt);
if (btf_id == xdp_hints_rx_time.btf_type_id) {
print_meta_info_time_faster(pkt, &xdp_hints_rx_time);
} else if (btf_id == meta_mark) {
print_meta_info_mark(pkt);
}

1
AF_XDP-interaction/lib_xsk_extend.c
View File

@@ -166,7 +166,6 @@ void xsk_btf__free_xdp_hint(struct xsk_btf_info *xbi)
return;
__xsk_btf_free_hash(xbi);
btf__free(xbi->btf);
free(xbi);
}