selftests/bpf: Add test for sk->sk_bypass_prot_mem.
The test does the following for IPv4/IPv6 x TCP/UDP sockets
with/without sk->sk_bypass_prot_mem, which can be turned on by
net.core.bypass_prot_mem or bpf_setsockopt(SK_BPF_BYPASS_PROT_MEM).
1. Create socket pairs
2. Send NR_PAGES (32) of data (TCP consumes around 35 pages,
and UDP consuems 66 pages due to skb overhead)
3. Read memory_allocated from sk->sk_prot->memory_allocated and
sk->sk_prot->memory_per_cpu_fw_alloc
4. Check if unread data is charged to memory_allocated
If sk->sk_bypass_prot_mem is set, memory_allocated should not be
changed, but we allow a small error (up to 10 pages) in case
other processes on the host use some amounts of TCP/UDP memory.
The amount of allocated pages are buffered to per-cpu variable
{tcp,udp}_memory_per_cpu_fw_alloc up to +/- net.core.mem_pcpu_rsv
before reported to {tcp,udp}_memory_allocated.
At 3., memory_allocated is calculated from the 2 variables at
fentry of socket create function.
We drain the receive queue only for UDP before close() because UDP
recv queue is destroyed after RCU grace period. When I printed
memory_allocated, UDP bypass cases sometimes saw the no-bypass
case's leftover, but it's still in the small error range (<10 pages).
bpf_trace_printk: memory_allocated: 0 <-- TCP no-bypass
bpf_trace_printk: memory_allocated: 35
bpf_trace_printk: memory_allocated: 0 <-- TCP w/ sysctl
bpf_trace_printk: memory_allocated: 0
bpf_trace_printk: memory_allocated: 0 <-- TCP w/ bpf
bpf_trace_printk: memory_allocated: 0
bpf_trace_printk: memory_allocated: 0 <-- UDP no-bypass
bpf_trace_printk: memory_allocated: 66
bpf_trace_printk: memory_allocated: 2 <-- UDP w/ sysctl (2 pages leftover)
bpf_trace_printk: memory_allocated: 2
bpf_trace_printk: memory_allocated: 2 <-- UDP w/ bpf (2 pages leftover)
bpf_trace_printk: memory_allocated: 2
We prefer finishing tests faster than oversleeping for call_rcu()
+ sk_destruct().
The test completes within 2s on QEMU (64 CPUs) w/ KVM.
# time ./test_progs -t sk_bypass
#371/1 sk_bypass_prot_mem/TCP :OK
#371/2 sk_bypass_prot_mem/UDP :OK
#371/3 sk_bypass_prot_mem/TCPv6:OK
#371/4 sk_bypass_prot_mem/UDPv6:OK
#371 sk_bypass_prot_mem:OK
Summary: 1/4 PASSED, 0 SKIPPED, 0 FAILED
real 0m1.481s
user 0m0.181s
sys 0m0.441s
Signed-off-by: Kuniyuki Iwashima <kuniyu@google.com>
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Acked-by: Roman Gushchin <roman.gushchin@linux.dev>
Link: https://patch.msgid.link/20251014235604.3057003-7-kuniyu@google.com
2 files changed
