A packet that reaches gre_rcv() and does not belong to any tunnel is dropped, after an ICMP port unreachable is sent back, with a plain kfree_skb(). This is the GRE counterpart of a UDP packet hitting no socket, and by far the most common way a GRE packet is dropped on receive, yet nothing tells it apart from a malformed one.
Add SKB_DROP_REASON_GRE_TUNNEL_NOT_FOUND for it, in the spirit of the existing SKB_DROP_REASON_VXLAN_VNI_NOT_FOUND, and report it from erspan_rcv() and __ipgre_rcv() through a new output parameter, so that a failed lookup is not reported the same way as a header that could not be pulled or as a metadata allocation failure. The header pull failures reuse SKB_DROP_REASON_HDR_TRUNC and the metadata allocation failures reuse SKB_DROP_REASON_NOMEM. Assisted-by: Claude-Code:claude-opus-5 Signed-off-by: Anton Danilov <[email protected]> --- include/net/dropreason-core.h | 6 ++++++ net/ipv4/ip_gre.c | 37 +++++++++++++++++++++++------------ 2 files changed, 30 insertions(+), 13 deletions(-) diff --git a/include/net/dropreason-core.h b/include/net/dropreason-core.h index 8efa682601f0..d1fb52c1b0cb 100644 --- a/include/net/dropreason-core.h +++ b/include/net/dropreason-core.h @@ -132,6 +132,7 @@ FN(IP_TUNNEL_OLD_SEQ) \ FN(GRE_INVALID_HDR) \ FN(GRE_CSUM) \ + FN(GRE_TUNNEL_NOT_FOUND) \ FNe(MAX) /** @@ -631,6 +632,11 @@ enum skb_drop_reason { SKB_DROP_REASON_GRE_INVALID_HDR, /** @SKB_DROP_REASON_GRE_CSUM: GRE checksum error */ SKB_DROP_REASON_GRE_CSUM, + /** + * @SKB_DROP_REASON_GRE_TUNNEL_NOT_FOUND: no GRE tunnel found for the + * endpoints and the key the packet carries. + */ + SKB_DROP_REASON_GRE_TUNNEL_NOT_FOUND, /** * @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/net/ipv4/ip_gre.c b/net/ipv4/ip_gre.c index 1894c5746a73..4d9bb6d186ae 100644 --- a/net/ipv4/ip_gre.c +++ b/net/ipv4/ip_gre.c @@ -265,7 +265,7 @@ static bool is_erspan_type1(int gre_hdr_len) } static int erspan_rcv(struct sk_buff *skb, struct tnl_ptk_info *tpi, - int gre_hdr_len) + int gre_hdr_len, enum skb_drop_reason *reason) { struct net *net = dev_net(skb->dev); struct metadata_dst *tun_dst = NULL; @@ -289,8 +289,10 @@ static int erspan_rcv(struct sk_buff *skb, struct tnl_ptk_info *tpi, iph->saddr, iph->daddr, 0); } else { if (unlikely(!pskb_may_pull(skb, - gre_hdr_len + sizeof(*ershdr)))) + gre_hdr_len + sizeof(*ershdr)))) { + *reason = SKB_DROP_REASON_HDR_TRUNC; return PACKET_REJECT; + } ershdr = (struct erspan_base_hdr *)(skb->data + gre_hdr_len); ver = ershdr->ver; @@ -306,8 +308,10 @@ static int erspan_rcv(struct sk_buff *skb, struct tnl_ptk_info *tpi, else len = gre_hdr_len + erspan_hdr_len(ver); - if (unlikely(!pskb_may_pull(skb, len))) + if (unlikely(!pskb_may_pull(skb, len))) { + *reason = SKB_DROP_REASON_HDR_TRUNC; return PACKET_REJECT; + } if (__iptunnel_pull_header(skb, len, @@ -327,8 +331,10 @@ static int erspan_rcv(struct sk_buff *skb, struct tnl_ptk_info *tpi, tun_dst = ip_tun_rx_dst(skb, flags, tun_id, sizeof(*md)); - if (!tun_dst) + if (!tun_dst) { + *reason = SKB_DROP_REASON_NOMEM; return PACKET_REJECT; + } /* MUST set options_len before referencing options */ info = &tun_dst->u.tun_info; @@ -356,15 +362,17 @@ static int erspan_rcv(struct sk_buff *skb, struct tnl_ptk_info *tpi, ip_tunnel_rcv(tunnel, skb, tpi, tun_dst, log_ecn_error); return PACKET_RCVD; } + *reason = SKB_DROP_REASON_GRE_TUNNEL_NOT_FOUND; return PACKET_REJECT; drop: - kfree_skb(skb); + kfree_skb_reason(skb, SKB_DROP_REASON_HDR_TRUNC); return PACKET_RCVD; } static int __ipgre_rcv(struct sk_buff *skb, const struct tnl_ptk_info *tpi, - struct ip_tunnel_net *itn, int hdr_len, bool raw_proto) + struct ip_tunnel_net *itn, int hdr_len, bool raw_proto, + enum skb_drop_reason *reason) { struct metadata_dst *tun_dst = NULL; const struct iphdr *iph; @@ -400,22 +408,25 @@ static int __ipgre_rcv(struct sk_buff *skb, const struct tnl_ptk_info *tpi, tun_id = key32_to_tunnel_id(tpi->key); tun_dst = ip_tun_rx_dst(skb, flags, tun_id, 0); - if (!tun_dst) + if (!tun_dst) { + *reason = SKB_DROP_REASON_NOMEM; return PACKET_REJECT; + } } ip_tunnel_rcv(tunnel, skb, tpi, tun_dst, log_ecn_error); return PACKET_RCVD; } + *reason = SKB_DROP_REASON_GRE_TUNNEL_NOT_FOUND; return PACKET_NEXT; drop: - kfree_skb(skb); + kfree_skb_reason(skb, SKB_DROP_REASON_HDR_TRUNC); return PACKET_RCVD; } static int ipgre_rcv(struct sk_buff *skb, const struct tnl_ptk_info *tpi, - int hdr_len) + int hdr_len, enum skb_drop_reason *reason) { struct net *net = dev_net(skb->dev); struct ip_tunnel_net *itn; @@ -426,13 +437,13 @@ static int ipgre_rcv(struct sk_buff *skb, const struct tnl_ptk_info *tpi, else itn = net_generic(net, ipgre_net_id); - res = __ipgre_rcv(skb, tpi, itn, hdr_len, false); + res = __ipgre_rcv(skb, tpi, itn, hdr_len, false, reason); if (res == PACKET_NEXT && tpi->proto == htons(ETH_P_TEB)) { /* ipgre tunnels in collect metadata mode should receive * also ETH_P_TEB traffic. */ itn = net_generic(net, ipgre_net_id); - res = __ipgre_rcv(skb, tpi, itn, hdr_len, true); + res = __ipgre_rcv(skb, tpi, itn, hdr_len, true, reason); } return res; } @@ -457,12 +468,12 @@ static int gre_rcv(struct sk_buff *skb) 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, hdr_len, &reason) == PACKET_RCVD) return 0; goto out; } - if (ipgre_rcv(skb, &tpi, hdr_len) == PACKET_RCVD) + if (ipgre_rcv(skb, &tpi, hdr_len, &reason) == PACKET_RCVD) return 0; out: -- 2.47.3
