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tcp: Simplify tcp_set_congestion_control() load=false case 

Simplify tcp_set_congestion_control() by removing the initialization
code path for the !load case.

There are only two call sites for tcp_set_congestion_control(). The
EBPF call site is the only one that passes load=false; it also passes
cap_net_admin=true. Because of that, the exact same behavior can be
achieved by removing the special if (!load) branch of the logic. Both
before and after this commit, the EBPF case will call
bpf_try_module_get(), and if that succeeds then call
tcp_reinit_congestion_control() or if that fails then return EBUSY.

Note that this returns the logic to a structure very similar to the
structure before:
  commit 91b5b21c7c ("bpf: Add support for changing congestion control")
except that the CAP_NET_ADMIN status is passed in as a function
argument.

This clean-up was suggested by Martin KaFai Lau.

Suggested-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Cc: Lawrence Brakmo <brakmo@fb.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Yuchung Cheng <ycheng@google.com>
Cc: Kevin Yang <yyd@google.com>
This commit is contained in:
Neal Cardwell 2020-09-10 15:35:36 -04:00 committed by Alexei Starovoitov
parent 5cdc744caa
commit 5050bef873
1 changed files with 4 additions and 11 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

15
net/ipv4/tcp_cong.c
View File

@ -362,21 +362,14 @@ int tcp_set_congestion_control(struct sock *sk, const char *name, bool load,
goto out;
}
if (!ca) {
if (!ca)
err = -ENOENT;
} else if (!load) {
if (bpf_try_module_get(ca, ca->owner)) {
tcp_reinit_congestion_control(sk, ca);
} else {
err = -EBUSY;
}
} else if (!((ca->flags & TCP_CONG_NON_RESTRICTED) || cap_net_admin)) {
else if (!((ca->flags & TCP_CONG_NON_RESTRICTED) || cap_net_admin))
err = -EPERM;
} else if (!bpf_try_module_get(ca, ca->owner)) {
else if (!bpf_try_module_get(ca, ca->owner))
err = -EBUSY;
} else {
else
tcp_reinit_congestion_control(sk, ca);
}
out:
rcu_read_unlock();
return err;