selftests: drv-net: Test head-adjustment support

Add test to validate the headroom adjustment support for both extension
and the shrinking cases. For the extension part, eat up space from
the start of payload data whereas, for the shrinking part, populate
the newly available space with a tag. In the user-space, validate that a
test string is manipulated accordingly.
The negative and positive offset values result in shrinking and growing of
headroom (growing and shrinking of payload) respectively.

TAP version 13
1..9
ok 1 xdp.test_xdp_native_pass_sb
ok 2 xdp.test_xdp_native_pass_mb
ok 3 xdp.test_xdp_native_drop_sb
ok 4 xdp.test_xdp_native_drop_mb
ok 5 xdp.test_xdp_native_tx_mb
\# Failed run: pkt_sz 512, ... offset 1. Reason: Adjustment failed
ok 6 xdp.test_xdp_native_adjst_tail_grow_data
ok 7 xdp.test_xdp_native_adjst_tail_shrnk_data
\# Failed run: pkt_sz 512, ... offset -128. Reason: Adjustment failed
ok 8 xdp.test_xdp_native_adjst_head_grow_data
\# Failed run: pkt_sz (512) > HDS threshold (0) and offset 64 > 48
ok 9 xdp.test_xdp_native_adjst_head_shrnk_data
\# Totals: pass:9 fail:0 xfail:0 xpass:0 skip:0 error:0

Signed-off-by: Mohsin Bashir <mohsin.bashr@gmail.com>
Link: https://patch.msgid.link/20250719083059.3209169-6-mohsin.bashr@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

1 files changed, 146 insertions, 1 deletions

diff --git a/tools/testing/selftests/drivers/net/xdp.py b/tools/testing/selftests/drivers/net/xdp.py
index 85b5db0a1121..887d662ad128 100755
--- a/tools/testing/selftests/drivers/net/xdp.py
+++ b/tools/testing/selftests/drivers/net/xdp.py
@@ -12,7 +12,7 @@ from dataclasses import dataclass
 from enum import Enum
 
 from lib.py import ksft_run, ksft_exit, ksft_eq, ksft_ne, ksft_pr
-from lib.py import KsftFailEx, NetDrvEpEnv
+from lib.py import KsftFailEx, NetDrvEpEnv, EthtoolFamily, NlError
 from lib.py import bkg, cmd, rand_port
 from lib.py import ip, bpftool, defer
 
@@ -31,6 +31,7 @@ class XDPAction(Enum):
     DROP = 1  # Drop the packet
     TX = 2    # Route the packet to the remote host
     TAIL_ADJST = 3  # Adjust the tail of the packet
+    HEAD_ADJST = 4  # Adjust the head of the packet
 
 
 class XDPStats(Enum):
@@ -483,6 +484,147 @@ def test_xdp_native_adjst_tail_shrnk_data(cfg):
     _validate_res(res, offset_lst, pkt_sz_lst)
 
 
+def get_hds_thresh(cfg):
+    """
+    Retrieves the header data split (HDS) threshold for a network interface.
+
+    Args:
+        cfg: Configuration object containing network settings.
+
+    Returns:
+        The HDS threshold value. If the threshold is not supported or an error occurs,
+        a default value of 1500 is returned.
+    """
+    netnl = cfg.netnl
+    hds_thresh = 1500
+
+    try:
+        rings = netnl.rings_get({'header': {'dev-index': cfg.ifindex}})
+        if 'hds-thresh' not in rings:
+            ksft_pr(f'hds-thresh not supported. Using default: {hds_thresh}')
+            return hds_thresh
+        hds_thresh = rings['hds-thresh']
+    except NlError as e:
+        ksft_pr(f"Failed to get rings: {e}. Using default: {hds_thresh}")
+
+    return hds_thresh
+
+
+def _test_xdp_native_head_adjst(cfg, prog, pkt_sz_lst, offset_lst):
+    """
+    Tests the XDP head adjustment action for a multi-buffer case.
+
+    Args:
+        cfg: Configuration object containing network settings.
+        netnl: Network namespace or link object (not used in this function).
+
+    This function sets up the packet size and offset lists, then performs
+    the head adjustment test by sending and receiving UDP packets.
+    """
+    cfg.require_cmd("socat", remote=True)
+
+    prog_info = _load_xdp_prog(cfg, BPFProgInfo(prog, "xdp_native.bpf.o", "xdp.frags", 9000))
+    port = rand_port()
+
+    _set_xdp_map("map_xdp_setup", TestConfig.MODE.value, XDPAction.HEAD_ADJST.value)
+    _set_xdp_map("map_xdp_setup", TestConfig.PORT.value, port)
+
+    hds_thresh = get_hds_thresh(cfg)
+    for offset in offset_lst:
+        for pkt_sz in pkt_sz_lst:
+            # The "head" buffer must contain at least the Ethernet header
+            # after we eat into it. We send large-enough packets, but if HDS
+            # is enabled head will only contain headers. Don't try to eat
+            # more than 28 bytes (UDPv4 + eth hdr left: (14 + 20 + 8) - 14)
+            l2_cut_off = 28 if cfg.addr_ipver == 4 else 48
+            if pkt_sz > hds_thresh and offset > l2_cut_off:
+                ksft_pr(
+                f"Failed run: pkt_sz ({pkt_sz}) > HDS threshold ({hds_thresh}) and "
+                f"offset {offset} > {l2_cut_off}"
+                )
+                return {"status": "pass"}
+
+            test_str = ''.join(random.choice(string.ascii_lowercase) for _ in range(pkt_sz))
+            tag = format(random.randint(65, 90), '02x')
+
+            _set_xdp_map("map_xdp_setup",
+                     TestConfig.ADJST_OFFSET.value,
+                     offset)
+            _set_xdp_map("map_xdp_setup", TestConfig.ADJST_TAG.value, int(tag, 16))
+            _set_xdp_map("map_xdp_setup", TestConfig.ADJST_OFFSET.value, offset)
+
+            recvd_str = _exchg_udp(cfg, port, test_str)
+
+            # Check for failures around adjustment and data exchange
+            failure = _check_for_failures(recvd_str, _get_stats(prog_info['maps']['map_xdp_stats']))
+            if failure is not None:
+                return {
+                    "status": "fail",
+                    "reason": failure,
+                    "offset": offset,
+                    "pkt_sz": pkt_sz
+                }
+
+            # Validate data content based on offset direction
+            expected_data = None
+            if offset < 0:
+                expected_data = chr(int(tag, 16)) * (0 - offset) + test_str
+            else:
+                expected_data = test_str[offset:]
+
+            if recvd_str != expected_data:
+                return {
+                    "status": "fail",
+                    "reason": "Data mismatch",
+                    "offset": offset,
+                    "pkt_sz": pkt_sz
+                }
+
+    return {"status": "pass"}
+
+
+def test_xdp_native_adjst_head_grow_data(cfg):
+    """
+    Tests the XDP headroom growth support.
+
+    Args:
+        cfg: Configuration object containing network settings.
+
+    This function sets up the packet size and offset lists, then calls the
+    _test_xdp_native_head_adjst_mb function to perform the actual test. The
+    test is passed if the headroom is successfully extended for given packet
+    sizes and offsets.
+    """
+    pkt_sz_lst = [512, 1024, 2048]
+
+    # Negative values result in headroom shrinking, resulting in growing of payload
+    offset_lst = [-16, -32, -64, -128, -256]
+    res = _test_xdp_native_head_adjst(cfg, "xdp_prog_frags", pkt_sz_lst, offset_lst)
+
+    _validate_res(res, offset_lst, pkt_sz_lst)
+
+
+def test_xdp_native_adjst_head_shrnk_data(cfg):
+    """
+    Tests the XDP headroom shrinking support.
+
+    Args:
+        cfg: Configuration object containing network settings.
+
+    This function sets up the packet size and offset lists, then calls the
+    _test_xdp_native_head_adjst_mb function to perform the actual test. The
+    test is passed if the headroom is successfully shrunk for given packet
+    sizes and offsets.
+    """
+    pkt_sz_lst = [512, 1024, 2048]
+
+    # Positive values result in headroom growing, resulting in shrinking of payload
+    offset_lst = [16, 32, 64, 128, 256]
+    res = _test_xdp_native_head_adjst(cfg, "xdp_prog_frags", pkt_sz_lst, offset_lst)
+
+    _validate_res(res, offset_lst, pkt_sz_lst)
+
+
 def main():
     """
     Main function to execute the XDP tests.
@@ -493,6 +635,7 @@ def main():
     function to execute the tests.
     """
     with NetDrvEpEnv(__file__) as cfg:
+        cfg.netnl = EthtoolFamily()
         ksft_run(
             [
                 test_xdp_native_pass_sb,
@@ -502,6 +645,8 @@ def main():
                 test_xdp_native_tx_mb,
                 test_xdp_native_adjst_tail_grow_data,
                 test_xdp_native_adjst_tail_shrnk_data,
+                test_xdp_native_adjst_head_grow_data,
+                test_xdp_native_adjst_head_shrnk_data,
             ],
             args=(cfg,))
     ksft_exit()