STRUCT ETHTOOL_GSTRINGS(9)

💖 struct ethtool_gstrings(9) 💖

okay so this is a page from the Kernel API Manual — yes, the kernel has a manual, and yes it's kinda iconic. buckle up bestie, we're talking about the little struct that holds your string sets for data tagging 🎀

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✨ NAME ✨

struct ethtool_gstrings — the string set for data tagging. that's it, that's the vibe 🦋

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✨ SYNOPSIS ✨

struct ethtool_gstrings {
    __u32 cmd;
    __u32 string_set;
    __u32 len;
    __u8 data[];
 };

look at her. four fields and a dream 🌸

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✨ Members ✨

• cmd — the command number, and it is literally ETHTOOL_GSTRINGS. no notes, it just is 💅
• string_set — the string set ID. it's one of enum ethtool_stringset, so pick from the menu, don't freestyle 🙈
• len — how many strings live in the string set. the headcount, basically 👑
• data — the buffer where the strings actually go. each string is null-padded out to a size of ETH_GSTRING_LEN. so they all line up cute and even 💖

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✨ Description ✨

okay so the important part: users must use ETHTOOL_GSSET_INFO to find out how many strings are in the string set. like, don't guess. don't count on your fingers. ask. 🔥

then they must allocate a buffer of the appropriate size immediately following this structure. immediately after, bestie. the data field is a flexible array thing so it lives right there at the end 🧚

setting len on input is optional (though preferred — glow up and set it 💅), but if you're not setting it, it must be zeroed. otherwise. zeroed. got it? 😭

when it is set, len will return the requested count if it matches the actual count; otherwise, it will be zero. and the reason is genuinely so valid — this prevents issues when the number of strings is different than the userspace allocation. mismatch protection, we love to see it 🫶

ngl this is one of those "small detail, huge consequences" situations. zero your len if you're not setting it. no cap. 💀

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✨ SEE ALSO ✨

the kernel file ./include/uapi/linux/ethtool.h, plus this absolutely enormous friend group of related pages — she knows everyone 🌈

• struct ethtool_cmd(9)
• struct ethtool_drvinfo(9)
• struct ethtool_wolinfo(9)
• struct ethtool_regs(9)
• struct ethtool_eeprom(9)
• struct ethtool_eee(9)
• struct ethtool_modinfo(9)
• struct ethtool_coalesce(9)
• struct ethtool_ringparam(9)
• struct ethtool_channels(9)
• struct ethtool_pauseparam(9)
• enum ethtool_stringset(9)
• enum ethtool_mac_stats_src(9)
• enum ethtool_module_power_mode_policy(9)
• enum ethtool_module_power_mode(9)
• enum ethtool_c33_pse_ext_state(9)
• enum ethtool_c33_pse_ext_substate_mr_mps_valid(9)
• enum ethtool_c33_pse_ext_substate_error_condition(9)
• enum ethtool_c33_pse_ext_substate_mr_pse_enable(9)
• enum ethtool_c33_pse_ext_substate_option_detect_ted(9)
• enum ethtool_c33_pse_ext_substate_option_vport_lim(9)
• enum ethtool_c33_pse_ext_substate_ovld_detected(9)
• enum ethtool_c33_pse_ext_substate_power_not_available(9)
• enum ethtool_c33_pse_ext_substate_short_detected(9)
• enum ethtool_pse_types(9)
• enum ethtool_c33_pse_admin_state(9)
• enum ethtool_c33_pse_pw_d_status(9)
• enum ethtool_podl_pse_admin_state(9)
• enum ethtool_podl_pse_pw_d_status(9)
• enum ethtool_mm_verify_status(9)
• enum ethtool_module_fw_flash_status(9)
• struct ethtool_sset_info(9)
• enum ethtool_test_flags(9)
• struct ethtool_test(9)
• struct ethtool_stats(9)
• struct ethtool_perm_addr(9)
• struct ethtool_tcpip4_spec(9)
• struct ethtool_ah_espip4_spec(9)
• struct ethtool_usrip4_spec(9)
• struct ethtool_tcpip6_spec(9)
• struct ethtool_ah_espip6_spec(9)
• struct ethtool_usrip6_spec(9)
• struct ethtool_flow_ext(9)
• struct ethtool_rx_flow_spec(9)
• struct ethtool_rxnfc(9)
• struct ethtool_rxfh_indir(9)
• struct ethtool_rxfh(9)
• struct ethtool_rx_ntuple_flow_spec(9)
• struct ethtool_rx_ntuple(9)
• struct ethtool_dump(9)
• struct ethtool_get_features_block(9)
• struct ethtool_gfeatures(9)
• struct ethtool_set_features_block(9)
• struct ethtool_sfeatures(9)
• struct ethtool_ts_info(9)
• struct ethtool_per_queue_op(9)
• struct ethtool_fecparam(9)
• enum ethtool_fec_config_bits(9)
• struct ethtool_link_settings(9)
• enum phy_upstream(9)

like I said. she knows everyone. iykyk 💜

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and that's the page!! mwah 💋 this little beauty lives in the source tree at ./include/uapi/linux, and the version/date stamp on her is October 2026 — so yeah, she's from the future, main character energy only ⭐👑 hope that helped bestie, go forth and allocate your buffers correctly 🦋💖