[ upstream commit 9f492a1 ]

The Go's GC is unable to track objects referred by uintptr [1] [2].

A consequence of this is that the GC might collect such objects
when a blocking syscall is executed. This might corrupt memory of
other Go objects e.g. if the reclaimed memory is used for new objects and
the kernel modifies the objects in the context of the blocking syscall.

To prevent from this, we protect each pointer to objects with
runtime.KeepAlive() which marks the objects as alive at least until
runtime.KeepAlive() has been called.

[1]: golang/go#13372 (comment)
[2]: https://utcc.utoronto.ca/~cks/space/blog/programming/GoUintptrVsUnsafePointer

Co-developed-by: André Martins <andre@cilium.io>
Co-developed-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Martynas Pumputis <m@lambda.lt>
Signed-off-by: John Fastabend <john.fastabend@gmail.com>

[ upstream commit 4630078 ]

Fix the space hack which stopped working with make v4.3 (works with
v4.2 though):

    [..]
    " [-DENABLE_HOST_REDIRECT-DENABLE_IPV4-DENABLE_IPV6-DENABLE_NAT46]";
    clang -DENABLE_HOST_REDIRECT-DENABLE_IPV4-DENABLE_IPV6-DENABLE_NAT46
    -I/home/brb/sandbox/gopath/src/github.com/cilium/cilium/bpf/include
    -I/home/brb/sandbox/gopath/src/github.com/cilium/cilium/bpf
    -D__NR_CPUS__=8 -O2 -g -target bpf -emit-llvm -Wall -Werror
    -Wno-address-of-packed-member -Wno-unknown-warning-option -c bpf_lxc.c
    -o bpf_lxc.ll; llc -march=bpf -mcpu=probe -mattr=dwarfris -o /dev/null
    bpf_lxc.ll;  \
    fi
    In file included from <built-in>:323:
    <command line>:1:20: error: ISO C99 requires whitespace after the macro
    name [-Werror,-Wc99-extensions]
    #define ENABLE_IPV4-DHAVE_LPM_MAP_TYPE 1

Signed-off-by: Martynas Pumputis <m@lambda.lt>
Signed-off-by: John Fastabend <john.fastabend@gmail.com>