cherry-pick commits to 1.34.x#4229

Merged

menghanl merged 3 commits intogrpc:v1.34.xfrom

menghanl:v1.34.x

Mar 11, 2021

Commits on Feb 26, 2021

[v1.34.x] encoding/proto: do not panic when types do not match (#4218)
menghanl
committed

Commits on Mar 9, 2021

[v1.34.x] set path
menghanl
committed
[v1.34.x] xds: add env var protection for client-side security (#4247)

easwars
authored and
menghanl
committed