netbpfload: add back support for 4.9-T kernels
This effectively reverts aosp/2268766
Test: TreeHugger
Signed-off-by: Maciej Żenczykowski <maze@google.com>
Change-Id: I42da5c56fe4b69635b9678ff57ade7788c17f7c8
diff --git a/netbpfload/loader.cpp b/netbpfload/loader.cpp
index c534b2c..7754a3e 100644
--- a/netbpfload/loader.cpp
+++ b/netbpfload/loader.cpp
@@ -574,6 +574,14 @@
static bool mapMatchesExpectations(const unique_fd& fd, const string& mapName,
const struct bpf_map_def& mapDef, const enum bpf_map_type type) {
+ // bpfGetFd... family of functions require at minimum a 4.14 kernel,
+ // so on 4.9-T kernels just pretend the map matches our expectations.
+ // Additionally we'll get almost equivalent test coverage on newer devices/kernels.
+ // This is because the primary failure mode we're trying to detect here
+ // is either a source code misconfiguration (which is likely kernel independent)
+ // or a newly introduced kernel feature/bug (which is unlikely to get backported to 4.9).
+ if (!isAtLeastKernelVersion(4, 14, 0)) return true;
+
// Assuming fd is a valid Bpf Map file descriptor then
// all the following should always succeed on a 4.14+ kernel.
// If they somehow do fail, they'll return -1 (and set errno),
@@ -711,6 +719,16 @@
}
enum bpf_map_type type = md[i].type;
+ if (type == BPF_MAP_TYPE_DEVMAP && !isAtLeastKernelVersion(4, 14, 0)) {
+ // On Linux Kernels older than 4.14 this map type doesn't exist, but it can kind
+ // of be approximated: ARRAY has the same userspace api, though it is not usable
+ // by the same ebpf programs. However, that's okay because the bpf_redirect_map()
+ // helper doesn't exist on 4.9-T anyway (so the bpf program would fail to load,
+ // and thus needs to be tagged as 4.14+ either way), so there's nothing useful you
+ // could do with a DEVMAP anyway (that isn't already provided by an ARRAY)...
+ // Hence using an ARRAY instead of a DEVMAP simply makes life easier for userspace.
+ type = BPF_MAP_TYPE_ARRAY;
+ }
if (type == BPF_MAP_TYPE_DEVMAP_HASH && !isAtLeastKernelVersion(5, 4, 0)) {
// On Linux Kernels older than 5.4 this map type doesn't exist, but it can kind
// of be approximated: HASH has the same userspace visible api.