From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-lf2-f12.google.com (mail-lf2-f12.google.com [74.125.229.204]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id AD34D522EE1 for ; Wed, 30 Sep 2026 18:39:33 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=74.125.229.204 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790793575; cv=none; b=gESWU5ArHZ0r1Ca13Ui8+3EwhscuB+DW6x4MO9v6xDu0mJ7Zvk2saCHssLYjUWucvej90HBy8IcsJjt3Y/qvhwsqi5zjQUEClB2suq/xscIX1/DkCUL2keiiT6gPQTWQbAVebBb/iprUnvSq9WahG3GNRpXnokfBlWQI1maHmNw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790793575; c=relaxed/simple; bh=+30bnDy5M/EUZhuBwDo0pPqL7vfdoPWX4PnYaUfMYp8=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=iKjXi+Jibs9XvGaecp4WbtyzPw37pU2dlbAuHkqtaAGoxOWFGaKS8Srvid8mKj/N7ofzcVGNivym+Q5X69DBHp6IcQ3atyzNWU65qAs9fh0ZcptdIo1bNi92KqK+NUhE14T3g+iJA1pWMvFsl0710Y9gEQdAYrDFN+ajMUiIHeI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=SttzixYw; arc=none smtp.client-ip=74.125.229.204 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="SttzixYw" Received: by mail-lf2-f12.google.com with SMTP id 2adb3069b0e04-5ba3e27d525so861808e87.1 for ; Wed, 30 Sep 2026 11:39:33 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1790793572; x=1791398372; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to:content-type; bh=gn6c2o2h3AHgs5qHDPlcMW1OaN+cNQv/VRB050jtNvM=; b=SttzixYwQ/xCuoewsu+NSHPKI/4t08puLAfMRp4LVUDfkHf7OxRdzsXPC1zpZy3G8w J8gnrMAjZhWoAjMARuBAU+nAHrabB50mgKpH2npun0u6ZV+8luposevHWgtAz3LcZjMN VhJ+trd5Sh+CToalFzwPtn622wZ6m1mYQNJeAkpe3Fjpxe/0C2ooC39X8tjo1FE4/p0h +4L0RsD0Z9RL75yJgpkD2cWIZ92l4bMaadl/gz4fDhKEJ2tNhrDqou1A+7Q7pqRS0GPH 7UNh8OHN/yXIlUUVfwMoY9RDqohlvOIsy2o5HSbRaV0+YyW3AwJAs4D5xG1r3yC5g3yo EjUw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20260707; t=1790793572; x=1791398372; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-gg:x-gm-message-state:from :to:cc:subject:date:message-id:reply-to:content-type; bh=gn6c2o2h3AHgs5qHDPlcMW1OaN+cNQv/VRB050jtNvM=; b=DfJClslF6zaBgk74iAGtl5k8IUG++Ukmb5+U6oY/JNlgUztEentwm2Dm05zVQ2mfYP X2ZEH8E4b15qUJFidVoXSwGS8YONdEK9czevT56gyYh7QqZpWSNCYjaEu7YpWjXE+lsW 2acK0WE4vYFgD0RD0eMZq9R1I9WF806/4DjKzk4otF0HVw9tVBrc+iET8KUDm+2TvM9q a83bgdGtp8K5RmRNO98CoL7xLKTroFqVbLCWTUPudfbO0jV0rM6vX7hDwYnlOj5ZXmzP VWkvT5B40xzyDahETIoCxY571vuT28pWCbk4f/4Hm/0B/rRCjhhvG72i04RM4IrmmZVX O5Cw== X-Forwarded-Encrypted: i=1; AKwUvBxJVlttEcBzyoZTseA5dJK+XdZHlo3hF6PHC/nKT+bBNVmGaJKGOj4tagtkQ19zndMo9EYZq0+sLDgM+DQ=@vger.kernel.org X-Gm-Message-State: AFq9FYLzkXza1BZkDnu1/c6ZUl2Uz/rn+1T6OqvTGKlWrDKq9TDrGs9k hgI5HLtPvr1BrqAuzj0K2Cc6PERb8fl8IdbABX13uaBkz+Eu6b5WHWSv X-Gm-Gg: AYBFou2T1KQxwFrfZSiRxkvpsrOIEkECtQyNeItzEvDpvcqBJqgAoB4i9a1/D9lGUgo FH74nPWhlbElD/hTz54FPU8blBfHfsccrfWYPYZxgsiQ/lrZvvgvoG9AFq6AUSWj02wpPbKR/nB DPtrTF3xNZMWprihSA599dQwiKItc0T6mKn78gzlQWkbiYI92gW/8iRzK3omOvp9yOagkcWIYNs 1b9N+DsJCqQ5E/mLQl7mS1Vbyx6BP3Z3+L0GYG+7xAwCZ6hkiTpEZVu1/VBMGzT9r4oMy+gcOXo W3AQ4io1c0nXfM3ESu8TbeQCl1E2lbRZf+oxCWUMl7gTk/Skr/6EufWEVp/xfJrphzv8+x0FZeo IISeyO9gtQlVz0gCfenzExZB1arukfv8YdFqQIbDIUcxw7KgLHmmd58SI2OozIIi1ehVBwG3Om4 /nOib33PzyrWUy6JXKTstkoK/GMVVgPh09FLkflJi+o5ybwOH/r6ViTSoTz8UVJiKtl73crhTAk iQTm/5QTc5wKa0sCUt7uA9AdCu56/EEdtwuQbMRpe9c X-Received: by 2002:a05:6512:3986:b0:5b8:b419:b7b with SMTP id 2adb3069b0e04-5ba4060b8b8mr880713e87.49.1790793571660; Wed, 30 Sep 2026 11:39:31 -0700 (PDT) Received: from dau-home-pc.. ([212.35.169.181]) by smtp.gmail.com with ESMTPSA id 2adb3069b0e04-5ba42fbb999sm156593e87.62.2026.09.30.11.39.29 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 30 Sep 2026 11:39:31 -0700 (PDT) From: Anton Danilov To: netdev@vger.kernel.org Cc: "David S . Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , David Ahern , Ido Schimmel , Andrew Lunn , linux-kernel@vger.kernel.org Subject: [PATCH net-next v5 06/14] gre: make gre_parse_header() report a drop reason Date: Wed, 30 Sep 2026 21:39:02 +0300 Message-ID: <20260930183910.3151873-7-littlesmilingcloud@gmail.com> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260930183910.3151873-1-littlesmilingcloud@gmail.com> References: <20260930183910.3151873-1-littlesmilingcloud@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit gre_parse_header() returns -EINVAL for every failure and its receive callers turn that into a plain kfree_skb(). The only detail they could get so far was the csum_err flag, which none of them actually reads: both ip_gre and ip6_gre declare it, pass it in and then ignore it. Make gre_parse_header() return the drop reason instead, with SKB_NOT_DROPPED_YET for a valid header, and let the two receive paths report it. The header length it used to return is already stored in tpi->hdr_len, so the callers take it from there. The reasons are: - SKB_DROP_REASON_TUNNEL_INVALID_HDR, for a header carrying an unsupported version or the routing bit; its description gets a GRE example, - SKB_DROP_REASON_GRE_CSUM, a new reason for a checksum error, like the existing TCP_CSUM, UDP_CSUM, ICMP_CSUM and IP_CSUM, - the reason pskb_may_pull_reason() returns when the header cannot be pulled: SKB_DROP_REASON_PKT_TOO_SMALL for a short packet and SKB_DROP_REASON_NOMEM for an allocation failure. The byte that tells WCCPv1 from WCCPv2 is read with skb_header_pointer() instead, which only fails on a short packet, so that check returns SKB_DROP_REASON_PKT_TOO_SMALL. gre_rcv() in the demux reports SKB_DROP_REASON_TUNNEL_INVALID_HDR for a version it cannot dispatch at all, as gre_parse_header() does for a nonzero version in ip6_gre, which does not go through the demux. A valid version whose handler is not registered, such as PPTP, is reported as SKB_DROP_REASON_UNHANDLED_PROTO. csum_err had a second use: the ICMP error handlers pass NULL for it, so that a checksum failure does not reject the header and the rest of it is still parsed, as they only get a part of the original packet. That came with commit b0350d51f001 ("ip_gre: fix parsing gre header in ipgre_err") and becomes an explicit ignore_csum_err argument. The checksum is still computed either way. As the function is exported, the comment above it becomes a kernel-doc comment, which describes the argument. Tunnel lookup failures and the other drops of the receive handlers still report SKB_DROP_REASON_NOT_SPECIFIED at this point; the following patches convert them. The reason follows the rule of ip_tunnel_rcv(). gre_rcv() of the demux and of ip6_gre sets it in its first statement, so it is not initialized there; ip_gre's gre_rcv() initializes it, which its looped back multicast check relies on, as it drops before the header is parsed. All three store the result of a helper in the reason, so their drop labels fall back to SKB_DROP_REASON_NOT_SPECIFIED. Assisted-by: LLM Signed-off-by: Anton Danilov --- include/net/dropreason-core.h | 4 +++ include/net/gre.h | 5 +-- net/ipv4/gre_demux.c | 65 ++++++++++++++++++++++++----------- net/ipv4/ip_gre.c | 18 +++++----- net/ipv6/ip6_gre.c | 18 +++++----- 5 files changed, 70 insertions(+), 40 deletions(-) diff --git a/include/net/dropreason-core.h b/include/net/dropreason-core.h index 85aaa58c3ecb..0d963f18a21e 100644 --- a/include/net/dropreason-core.h +++ b/include/net/dropreason-core.h @@ -131,6 +131,7 @@ FN(RECURSION_LIMIT) \ FN(TUNNEL_OPT_MISMATCH) \ FN(TUNNEL_OLD_SEQ) \ + FN(GRE_CSUM) \ FNe(MAX) /** @@ -544,6 +545,7 @@ enum skb_drop_reason { * @SKB_DROP_REASON_TUNNEL_INVALID_HDR: tunnel header is invalid. E.g.: * 1) VXLAN reserved fields are not zero * 2) VXLAN "I" flag is not set + * 3) GRE version is not supported or the routing bit is set */ SKB_DROP_REASON_TUNNEL_INVALID_HDR, /** @@ -631,6 +633,8 @@ enum skb_drop_reason { * remote endpoint restarted and reset its sequence numbering. */ SKB_DROP_REASON_TUNNEL_OLD_SEQ, + /** @SKB_DROP_REASON_GRE_CSUM: GRE checksum error */ + SKB_DROP_REASON_GRE_CSUM, /** * @SKB_DROP_REASON_MAX: the maximum of core drop reasons, which * shouldn't be used as a real 'reason' - only for tracing code gen diff --git a/include/net/gre.h b/include/net/gre.h index b55f67ecd2fc..b5dbe00ab15e 100644 --- a/include/net/gre.h +++ b/include/net/gre.h @@ -32,8 +32,9 @@ struct gre_protocol { int gre_add_protocol(const struct gre_protocol *proto, u8 version); int gre_del_protocol(const struct gre_protocol *proto, u8 version); -int gre_parse_header(struct sk_buff *skb, struct tnl_ptk_info *tpi, - bool *csum_err, __be16 proto, int nhs); +enum skb_drop_reason +gre_parse_header(struct sk_buff *skb, struct tnl_ptk_info *tpi, + bool ignore_csum_err, __be16 proto, int nhs); static inline bool netif_is_gretap(const struct net_device *dev) { diff --git a/net/ipv4/gre_demux.c b/net/ipv4/gre_demux.c index 96fd7dc6d82d..fccdaa240f46 100644 --- a/net/ipv4/gre_demux.c +++ b/net/ipv4/gre_demux.c @@ -56,28 +56,47 @@ int gre_del_protocol(const struct gre_protocol *proto, u8 version) } EXPORT_SYMBOL_GPL(gre_del_protocol); -/* Fills in tpi and returns header length to be pulled. - * Note that caller must use pskb_may_pull() before pulling GRE header. +/** + * gre_parse_header() - parse the GRE header of a packet + * @skb: the packet; the GRE header starts @nhs bytes past skb->data + * @tpi: filled in with the fields of the header, and with the length of + * the header to be pulled in tpi->hdr_len + * @ignore_csum_err: do not reject the header when its checksum does not + * match. The ICMP error handlers set it, as they only get a part of the + * original packet; the checksum is still computed and the rest of the + * header is parsed. + * @proto: the protocol to report for a WCCP payload, ETH_P_IP or + * ETH_P_IPV6 + * @nhs: the offset of the GRE header from skb->data + * + * The caller must use pskb_may_pull() before pulling the GRE header. + * + * Return: SKB_NOT_DROPPED_YET, or the reason to drop the packet if the + * header is rejected. */ -int gre_parse_header(struct sk_buff *skb, struct tnl_ptk_info *tpi, - bool *csum_err, __be16 proto, int nhs) +enum skb_drop_reason +gre_parse_header(struct sk_buff *skb, struct tnl_ptk_info *tpi, + bool ignore_csum_err, __be16 proto, int nhs) { const struct gre_base_hdr *greh; + enum skb_drop_reason reason; __be32 *options; int hdr_len; - if (unlikely(!pskb_may_pull(skb, nhs + sizeof(struct gre_base_hdr)))) - return -EINVAL; + reason = pskb_may_pull_reason(skb, nhs + sizeof(struct gre_base_hdr)); + if (unlikely(reason)) + return reason; greh = (struct gre_base_hdr *)(skb->data + nhs); if (unlikely(greh->flags & (GRE_VERSION | GRE_ROUTING))) - return -EINVAL; + return SKB_DROP_REASON_TUNNEL_INVALID_HDR; gre_flags_to_tnl_flags(tpi->flags, greh->flags); hdr_len = gre_calc_hlen(tpi->flags); - if (!pskb_may_pull(skb, nhs + hdr_len)) - return -EINVAL; + reason = pskb_may_pull_reason(skb, nhs + hdr_len); + if (reason) + return reason; greh = (struct gre_base_hdr *)(skb->data + nhs); tpi->proto = greh->protocol; @@ -87,9 +106,8 @@ int gre_parse_header(struct sk_buff *skb, struct tnl_ptk_info *tpi, if (!skb_checksum_simple_validate(skb)) { skb_checksum_try_convert(skb, IPPROTO_GRE, null_compute_pseudo); - } else if (csum_err) { - *csum_err = true; - return -EINVAL; + } else if (!ignore_csum_err) { + return SKB_DROP_REASON_GRE_CSUM; } options++; @@ -117,7 +135,7 @@ int gre_parse_header(struct sk_buff *skb, struct tnl_ptk_info *tpi, val = skb_header_pointer(skb, nhs + hdr_len, sizeof(_val), &_val); if (!val) - return -EINVAL; + return SKB_DROP_REASON_PKT_TOO_SMALL; tpi->proto = proto; if ((*val & 0xF0) != 0x40) hdr_len += 4; @@ -132,29 +150,35 @@ int gre_parse_header(struct sk_buff *skb, struct tnl_ptk_info *tpi, greh->protocol == htons(ETH_P_ERSPAN2)) { struct erspan_base_hdr *ershdr; - if (!pskb_may_pull(skb, nhs + hdr_len + sizeof(*ershdr))) - return -EINVAL; + reason = pskb_may_pull_reason(skb, + nhs + hdr_len + sizeof(*ershdr)); + if (reason) + return reason; ershdr = (struct erspan_base_hdr *)(skb->data + nhs + hdr_len); tpi->key = cpu_to_be32(get_session_id(ershdr)); } - return hdr_len; + return SKB_NOT_DROPPED_YET; } EXPORT_SYMBOL(gre_parse_header); static int gre_rcv(struct sk_buff *skb) { const struct gre_protocol *proto; + enum skb_drop_reason reason; u8 ver; int ret; - if (!pskb_may_pull(skb, 12)) + reason = pskb_may_pull_reason(skb, 12); + if (reason) goto drop; ver = skb->data[1]&0x7f; - if (ver >= GREPROTO_MAX) + if (ver >= GREPROTO_MAX) { + reason = SKB_DROP_REASON_TUNNEL_INVALID_HDR; goto drop; + } rcu_read_lock(); proto = rcu_dereference(gre_proto[ver]); @@ -167,11 +191,12 @@ static int gre_rcv(struct sk_buff *skb) drop_nohandler: rcu_read_unlock(); dev_core_stats_rx_nohandler_inc(skb->dev); - kfree_skb(skb); + kfree_skb_reason(skb, SKB_DROP_REASON_UNHANDLED_PROTO); return NET_RX_DROP; drop: + reason = reason ?: SKB_DROP_REASON_NOT_SPECIFIED; dev_core_stats_rx_dropped_inc(skb->dev); - kfree_skb(skb); + kfree_skb_reason(skb, reason); return NET_RX_DROP; } diff --git a/net/ipv4/ip_gre.c b/net/ipv4/ip_gre.c index 3ee437fa3eae..a1b44007b1d7 100644 --- a/net/ipv4/ip_gre.c +++ b/net/ipv4/ip_gre.c @@ -237,8 +237,8 @@ static void gre_err(struct sk_buff *skb, u32 info) const int code = icmp_hdr(skb)->code; struct tnl_ptk_info tpi; - if (gre_parse_header(skb, &tpi, NULL, htons(ETH_P_IP), - iph->ihl * 4) < 0) + if (gre_parse_header(skb, &tpi, true, htons(ETH_P_IP), + iph->ihl * 4)) return; if (type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED) { @@ -439,9 +439,8 @@ static int ipgre_rcv(struct sk_buff *skb, const struct tnl_ptk_info *tpi, static int gre_rcv(struct sk_buff *skb) { + enum skb_drop_reason reason = SKB_DROP_REASON_NOT_SPECIFIED; struct tnl_ptk_info tpi; - bool csum_err = false; - int hdr_len; #ifdef CONFIG_NET_IPGRE_BROADCAST if (ipv4_is_multicast(ip_hdr(skb)->daddr)) { @@ -451,25 +450,26 @@ static int gre_rcv(struct sk_buff *skb) } #endif - hdr_len = gre_parse_header(skb, &tpi, &csum_err, htons(ETH_P_IP), 0); - if (hdr_len < 0) + reason = gre_parse_header(skb, &tpi, false, htons(ETH_P_IP), 0); + if (reason) goto drop; if (unlikely(tpi.proto == htons(ETH_P_ERSPAN) || tpi.proto == htons(ETH_P_ERSPAN2))) { - if (erspan_rcv(skb, &tpi, hdr_len) == PACKET_RCVD) + if (erspan_rcv(skb, &tpi, tpi.hdr_len) == PACKET_RCVD) return 0; goto out; } - if (ipgre_rcv(skb, &tpi, hdr_len) == PACKET_RCVD) + if (ipgre_rcv(skb, &tpi, tpi.hdr_len) == PACKET_RCVD) return 0; out: icmp_send(skb, ICMP_DEST_UNREACH, ICMP_PORT_UNREACH, 0); drop: + reason = reason ?: SKB_DROP_REASON_NOT_SPECIFIED; dev_core_stats_rx_dropped_inc(skb->dev); - kfree_skb(skb); + kfree_skb_reason(skb, reason); return 0; } diff --git a/net/ipv6/ip6_gre.c b/net/ipv6/ip6_gre.c index 0392f6ba862b..25fd290082c4 100644 --- a/net/ipv6/ip6_gre.c +++ b/net/ipv6/ip6_gre.c @@ -389,8 +389,8 @@ static int ip6gre_err(struct sk_buff *skb, struct inet6_skb_parm *opt, struct tnl_ptk_info tpi; struct ip6_tnl *t; - if (gre_parse_header(skb, &tpi, NULL, htons(ETH_P_IPV6), - offset) < 0) + if (gre_parse_header(skb, &tpi, true, htons(ETH_P_IPV6), + offset)) return -EINVAL; ipv6h = (const struct ipv6hdr *)skb->data; @@ -566,20 +566,19 @@ static int ip6erspan_rcv(struct sk_buff *skb, static int gre_rcv(struct sk_buff *skb) { + enum skb_drop_reason reason; struct tnl_ptk_info tpi; - bool csum_err = false; - int hdr_len; - hdr_len = gre_parse_header(skb, &tpi, &csum_err, htons(ETH_P_IPV6), 0); - if (hdr_len < 0) + reason = gre_parse_header(skb, &tpi, false, htons(ETH_P_IPV6), 0); + if (reason) goto drop; - if (iptunnel_pull_header(skb, hdr_len, tpi.proto, false)) + if (iptunnel_pull_header(skb, tpi.hdr_len, tpi.proto, false)) goto drop; if (unlikely(tpi.proto == htons(ETH_P_ERSPAN) || tpi.proto == htons(ETH_P_ERSPAN2))) { - if (ip6erspan_rcv(skb, &tpi, hdr_len) == PACKET_RCVD) + if (ip6erspan_rcv(skb, &tpi, tpi.hdr_len) == PACKET_RCVD) return 0; goto out; } @@ -590,8 +589,9 @@ static int gre_rcv(struct sk_buff *skb) out: icmpv6_send(skb, ICMPV6_DEST_UNREACH, ICMPV6_PORT_UNREACH, 0); drop: + reason = reason ?: SKB_DROP_REASON_NOT_SPECIFIED; dev_core_stats_rx_dropped_inc(skb->dev); - kfree_skb(skb); + kfree_skb_reason(skb, reason); return 0; } -- 2.47.3