cregit-Linux how code gets into the kernel

Release 4.15 net/ipv6/mcast_snoop.c

Directory: net/ipv6
/* Copyright (C) 2010: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>
 * Copyright (C) 2015: Linus Lüssing <linus.luessing@c0d3.blue>
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of version 2 of the GNU General Public
 * License as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, see <http://www.gnu.org/licenses/>.
 *
 *
 * Based on the MLD support added to br_multicast.c by YOSHIFUJI Hideaki.
 */

#include <linux/skbuff.h>
#include <net/ipv6.h>
#include <net/mld.h>
#include <net/addrconf.h>
#include <net/ip6_checksum.h>


static int ipv6_mc_check_ip6hdr(struct sk_buff *skb) { const struct ipv6hdr *ip6h; unsigned int len; unsigned int offset = skb_network_offset(skb) + sizeof(*ip6h); if (!pskb_may_pull(skb, offset)) return -EINVAL; ip6h = ipv6_hdr(skb); if (ip6h->version != 6) return -EINVAL; len = offset + ntohs(ip6h->payload_len); if (skb->len < len || len <= offset) return -EINVAL; return 0; }

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static int ipv6_mc_check_exthdrs(struct sk_buff *skb) { const struct ipv6hdr *ip6h; int offset; u8 nexthdr; __be16 frag_off; ip6h = ipv6_hdr(skb); if (ip6h->nexthdr != IPPROTO_HOPOPTS) return -ENOMSG; nexthdr = ip6h->nexthdr; offset = skb_network_offset(skb) + sizeof(*ip6h); offset = ipv6_skip_exthdr(skb, offset, &nexthdr, &frag_off); if (offset < 0) return -EINVAL; if (nexthdr != IPPROTO_ICMPV6) return -ENOMSG; skb_set_transport_header(skb, offset); return 0; }

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static int ipv6_mc_check_mld_reportv2(struct sk_buff *skb) { unsigned int len = skb_transport_offset(skb); len += sizeof(struct mld2_report); return pskb_may_pull(skb, len) ? 0 : -EINVAL; }

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static int ipv6_mc_check_mld_query(struct sk_buff *skb) { struct mld_msg *mld; unsigned int len = skb_transport_offset(skb); /* RFC2710+RFC3810 (MLDv1+MLDv2) require link-local source addresses */ if (!(ipv6_addr_type(&ipv6_hdr(skb)->saddr) & IPV6_ADDR_LINKLOCAL)) return -EINVAL; len += sizeof(struct mld_msg); if (skb->len < len) return -EINVAL; /* MLDv1? */ if (skb->len != len) { /* or MLDv2? */ len += sizeof(struct mld2_query) - sizeof(struct mld_msg); if (skb->len < len || !pskb_may_pull(skb, len)) return -EINVAL; } mld = (struct mld_msg *)skb_transport_header(skb); /* RFC2710+RFC3810 (MLDv1+MLDv2) require the multicast link layer * all-nodes destination address (ff02::1) for general queries */ if (ipv6_addr_any(&mld->mld_mca) && !ipv6_addr_is_ll_all_nodes(&ipv6_hdr(skb)->daddr)) return -EINVAL; return 0; }

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static int ipv6_mc_check_mld_msg(struct sk_buff *skb) { struct mld_msg *mld = (struct mld_msg *)skb_transport_header(skb); switch (mld->mld_type) { case ICMPV6_MGM_REDUCTION: case ICMPV6_MGM_REPORT: /* fall through */ return 0; case ICMPV6_MLD2_REPORT: return ipv6_mc_check_mld_reportv2(skb); case ICMPV6_MGM_QUERY: return ipv6_mc_check_mld_query(skb); default: return -ENOMSG; } }

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static inline __sum16 ipv6_mc_validate_checksum(struct sk_buff *skb) { return skb_checksum_validate(skb, IPPROTO_ICMPV6, ip6_compute_pseudo); }

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static int __ipv6_mc_check_mld(struct sk_buff *skb, struct sk_buff **skb_trimmed) { struct sk_buff *skb_chk = NULL; unsigned int transport_len; unsigned int len = skb_transport_offset(skb) + sizeof(struct mld_msg); int ret = -EINVAL; transport_len = ntohs(ipv6_hdr(skb)->payload_len); transport_len -= skb_transport_offset(skb) - sizeof(struct ipv6hdr); skb_chk = skb_checksum_trimmed(skb, transport_len, ipv6_mc_validate_checksum); if (!skb_chk) goto err; if (!pskb_may_pull(skb_chk, len)) goto err; ret = ipv6_mc_check_mld_msg(skb_chk); if (ret) goto err; if (skb_trimmed) *skb_trimmed = skb_chk; /* free now unneeded clone */ else if (skb_chk != skb) kfree_skb(skb_chk); ret = 0; err: if (ret && skb_chk && skb_chk != skb) kfree_skb(skb_chk); return ret; }

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/** * ipv6_mc_check_mld - checks whether this is a sane MLD packet * @skb: the skb to validate * @skb_trimmed: to store an skb pointer trimmed to IPv6 packet tail (optional) * * Checks whether an IPv6 packet is a valid MLD packet. If so sets * skb transport header accordingly and returns zero. * * -EINVAL: A broken packet was detected, i.e. it violates some internet * standard * -ENOMSG: IP header validation succeeded but it is not an MLD packet. * -ENOMEM: A memory allocation failure happened. * * Optionally, an skb pointer might be provided via skb_trimmed (or set it * to NULL): After parsing an MLD packet successfully it will point to * an skb which has its tail aligned to the IP packet end. This might * either be the originally provided skb or a trimmed, cloned version if * the skb frame had data beyond the IP packet. A cloned skb allows us * to leave the original skb and its full frame unchanged (which might be * desirable for layer 2 frame jugglers). * * Caller needs to set the skb network header and free any returned skb if it * differs from the provided skb. */
int ipv6_mc_check_mld(struct sk_buff *skb, struct sk_buff **skb_trimmed) { int ret; ret = ipv6_mc_check_ip6hdr(skb); if (ret < 0) return ret; ret = ipv6_mc_check_exthdrs(skb); if (ret < 0) return ret; return __ipv6_mc_check_mld(skb, skb_trimmed); }

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EXPORT_SYMBOL(ipv6_mc_check_mld);

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Directory: net/ipv6
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