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bpf: Add bpf_skc_to_tcp6_sock() helper

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The helper is used in tracing programs to cast a socket
pointer to a tcp6_sock pointer.
The return value could be NULL if the casting is illegal.

A new helper return type RET_PTR_TO_BTF_ID_OR_NULL is added
so the verifier is able to deduce proper return types for the helper.

Different from the previous BTF_ID based helpers,
the bpf_skc_to_tcp6_sock() argument can be several possible
btf_ids. More specifically, all possible socket data structures
with sock_common appearing in the first in the memory layout.
This patch only added socket types related to tcp and udp.

All possible argument btf_id and return value btf_id
for helper bpf_skc_to_tcp6_sock() are pre-calculcated and
cached. In the future, it is even possible to precompute
these btf_id's at kernel build time.

Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/bpf/20200623230809.3988195-1-yhs@fb.com
This commit is contained in:
Yonghong Song 2020-06-23 16:08:09 -07:00 • committed by Alexei Starovoitov
parent 72e2b2b66f
commit af7ec13833
8 changed files with 148 additions and 12 deletions
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2
scripts/bpf_helpers_doc.py
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@ -421,6 +421,7 @@ class PrinterHelpers(Printer):
'struct sockaddr',
'struct tcphdr',
'struct seq_file',
'struct tcp6_sock',
'struct __sk_buff',
'struct sk_msg_md',
@ -458,6 +459,7 @@ class PrinterHelpers(Printer):
'struct sockaddr',
'struct tcphdr',
'struct seq_file',
'struct tcp6_sock',
}
mapped_types = {
'u8': '__u8',