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dd21d1844a
In MLO scenarios, stations may have multiple links, each with distinct statistics. When userspace tools like iw or hostapd request station dumps, attempting to pack all per-link stats into a single netlink message can easily exceed the default 4KB buffer limit, especially when more than two links are active. This results in -EMSGSIZE errors and incomplete data delivery. To address this, fragment per-link station statistics across multiple netlink messages to ensure reliable delivery of complete MLO station information. Extend the stateful context with a two-phase dump mechanism: phase 0 (AGGREGATED) sends combined MLO-level statistics and phase 1 (PER_LINK) sends individual per-link statistics for each active link. The dump loop is structured to produce exactly one netlink message per iteration, with a common header (ifindex, wdev, mac, generation) built once and phase-specific payload added via a switch statement. This keeps header construction in one place and makes the EMSGSIZE bail-out uniform. Add a new request flag attribute, NL80211_ATTR_STA_DUMP_LINK_STATS (NLA_FLAG), for NL80211_CMD_GET_STATION dump. Userspace can set this flag to request per-link station statistics for MLO stations. Extract this flag during the first dump invocation by passing an attrbuf to nl80211_prepare_wdev_dump(); use __free(kfree) to avoid scattered manual kfree() calls. Cache the boolean in the dump context to avoid repeated parsing on subsequent invocations. Per-link messages carry a single NL80211_ATTR_MLO_LINKS nest with the link ID, link-specific MAC, and per-link NL80211_ATTR_STA_INFO payload. The link-specific validity (is_valid_ether_addr) and null pointer guard are checked in nl80211_put_link_station_payload() before any message construction begins. Also fix all nla_nest_start_noflag() calls in nl80211_fill_link_station() for nested attribute types (STA_INFO, BSS_PARAM, TID_STATS, per-tid) to use nla_nest_start() so the NLA_F_NESTED flag is set correctly. Propagate the actual return value from nl80211_put_sta_info_common() in the AGGREGATED phase rather than returning skb->len. Returning skb->len signals netlink to re-invoke the dump with the same sta_idx, causing an infinite loop when the aggregated payload is too large to fit; returning the real error code (-EMSGSIZE or otherwise) terminates the dump cleanly. Backward compatibility is seamlessly preserved for non-MLO stations. Signed-off-by: P Praneesh <praneesh.p@oss.qualcomm.com> Link: https://patch.msgid.link/20260614051739.3979947-5-praneesh.p@oss.qualcomm.com Signed-off-by: Johannes Berg <johannes.berg@intel.com>