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authorJohn Fastabend <john.fastabend@gmail.com>2018-12-16 15:47:04 -0800
committerDaniel Borkmann <daniel@iogearbox.net>2018-12-19 00:27:23 +0100
commit3bdbd0228e7555ec745e08469b98e5a0966409d6 (patch)
tree4a237a66574499f47d17fbcad4ad62f59384cfc1 /net/core
parent0bae2d4d62d523f06ff1a8e88ce38b45400acd28 (diff)
downloadlinux-3bdbd0228e7555ec745e08469b98e5a0966409d6.tar.bz2
bpf: sockmap, metadata support for reporting size of msg
This adds metadata to sk_msg_md for BPF programs to read the sk_msg size. When the SK_MSG program is running under an application that is using sendfile the data is not copied into sk_msg buffers by default. Rather the BPF program uses sk_msg_pull_data to read the bytes in. This avoids doing the costly memcopy instructions when they are not in fact needed. However, if we don't know the size of the sk_msg we have to guess if needed bytes are available by doing a pull request which may fail. By including the size of the sk_msg BPF programs can check the size before issuing sk_msg_pull_data requests. Additionally, the same applies for sendmsg calls when the application provides multiple iovs. Here the BPF program needs to pull in data to update data pointers but its not clear where the data ends without a size parameter. In many cases "guessing" is not easy to do and results in multiple calls to pull and without bounded loops everything gets fairly tricky. Clean this up by including a u32 size field. Note, all writes into sk_msg_md are rejected already from sk_msg_is_valid_access so nothing additional is needed there. Signed-off-by: John Fastabend <john.fastabend@gmail.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Diffstat (limited to 'net/core')
-rw-r--r--net/core/filter.c6
1 files changed, 6 insertions, 0 deletions
diff --git a/net/core/filter.c b/net/core/filter.c
index f9348806e843..3a3b21726fb5 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -7530,6 +7530,12 @@ static u32 sk_msg_convert_ctx_access(enum bpf_access_type type,
*insn++ = BPF_LDX_MEM(BPF_H, si->dst_reg, si->dst_reg,
offsetof(struct sock_common, skc_num));
break;
+
+ case offsetof(struct sk_msg_md, size):
+ *insn++ = BPF_LDX_MEM(BPF_FIELD_SIZEOF(struct sk_msg_sg, size),
+ si->dst_reg, si->src_reg,
+ offsetof(struct sk_msg_sg, size));
+ break;
}
return insn - insn_buf;