Commit 9a69e2b3 authored by Jakub Sitnicki's avatar Jakub Sitnicki Committed by Alexei Starovoitov
Browse files

bpf: Make remote_port field in struct bpf_sk_lookup 16-bit wide 



remote_port is another case of a BPF context field documented as a 32-bit
value in network byte order for which the BPF context access converter
generates a load of a zero-padded 16-bit integer in network byte order.

First such case was dst_port in bpf_sock which got addressed in commit
4421a582 ("bpf: Make dst_port field in struct bpf_sock 16-bit wide").

Loading 4-bytes from the remote_port offset and converting the value with
bpf_ntohl() leads to surprising results, as the expected value is shifted
by 16 bits.

Reduce the confusion by splitting the field in two - a 16-bit field holding
a big-endian integer, and a 16-bit zero-padding anonymous field that
follows it.

Suggested-by: default avatarAlexei Starovoitov <ast@kernel.org>
Signed-off-by: default avatarJakub Sitnicki <jakub@cloudflare.com>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20220209184333.654927-2-jakub@cloudflare.com
parent dc37dc61

include/uapi/linux/bpf.h

+2 −1
Original line number Diff line number Diff line
@@ -6453,7 +6453,8 @@ struct bpf_sk_lookup { 
	__u32 protocol;		/* IP protocol (IPPROTO_TCP, IPPROTO_UDP) */

	__u32 remote_ip4;	/* Network byte order */

	__u32 remote_ip6[4];	/* Network byte order */

	__u32 remote_port;	/* Network byte order */

	__be16 remote_port;	/* Network byte order */

	__u16 :16;		/* Zero padding */

	__u32 local_ip4;	/* Network byte order */

	__u32 local_ip6[4];	/* Network byte order */

	__u32 local_port;	/* Host byte order */

net/bpf/test_run.c

+2 −2
Original line number Diff line number Diff line
@@ -1147,7 +1147,7 @@ int bpf_prog_test_run_sk_lookup(struct bpf_prog *prog, const union bpf_attr *kat 
	if (!range_is_zero(user_ctx, offsetofend(typeof(*user_ctx), local_port), sizeof(*user_ctx)))

		goto out;



	if (user_ctx->local_port > U16_MAX || user_ctx->remote_port > U16_MAX) {

	if (user_ctx->local_port > U16_MAX) {

		ret = -ERANGE;

		goto out;

	}
@@ -1155,7 +1155,7 @@ int bpf_prog_test_run_sk_lookup(struct bpf_prog *prog, const union bpf_attr *kat 
	ctx.family = (u16)user_ctx->family;

	ctx.protocol = (u16)user_ctx->protocol;

	ctx.dport = (u16)user_ctx->local_port;

	ctx.sport = (__force __be16)user_ctx->remote_port;

	ctx.sport = user_ctx->remote_port;



	switch (ctx.family) {

	case AF_INET:

net/core/filter.c

+2 −1
Original line number Diff line number Diff line
@@ -10843,7 +10843,8 @@ static bool sk_lookup_is_valid_access(int off, int size, 
	case bpf_ctx_range(struct bpf_sk_lookup, local_ip4):

	case bpf_ctx_range_till(struct bpf_sk_lookup, remote_ip6[0], remote_ip6[3]):

	case bpf_ctx_range_till(struct bpf_sk_lookup, local_ip6[0], local_ip6[3]):

	case bpf_ctx_range(struct bpf_sk_lookup, remote_port):

	case offsetof(struct bpf_sk_lookup, remote_port) ...

	     offsetof(struct bpf_sk_lookup, local_ip4) - 1:

	case bpf_ctx_range(struct bpf_sk_lookup, local_port):

	case bpf_ctx_range(struct bpf_sk_lookup, ingress_ifindex):

		bpf_ctx_record_field_size(info, sizeof(__u32));