From 8bfcdf6671b1c8006c52c3eaf9fd1b5dfcf41c3d Mon Sep 17 00:00:00 2001 From: Pablo Neira Ayuso Date: Sun, 26 Oct 2014 12:35:54 +0100 Subject: [PATCH] netfilter: nf_reject_ipv6: split nf_send_reset6() in smaller functions That can be reused by the reject bridge expression to build the reject packet. The new functions are: * nf_reject_ip6_tcphdr_get(): to sanitize and to obtain the TCP header. * nf_reject_ip6hdr_put(): to build the IPv6 header. * nf_reject_ip6_tcphdr_put(): to build the TCP header. Signed-off-by: Pablo Neira Ayuso --- include/net/netfilter/ipv6/nf_reject.h | 10 ++ net/ipv6/netfilter/nf_reject_ipv6.c | 205 +++++++++++++++---------- 2 files changed, 134 insertions(+), 81 deletions(-) diff --git a/include/net/netfilter/ipv6/nf_reject.h b/include/net/netfilter/ipv6/nf_reject.h index 48e18810a9be..23216d48abf9 100644 --- a/include/net/netfilter/ipv6/nf_reject.h +++ b/include/net/netfilter/ipv6/nf_reject.h @@ -15,4 +15,14 @@ nf_send_unreach6(struct net *net, struct sk_buff *skb_in, unsigned char code, void nf_send_reset6(struct net *net, struct sk_buff *oldskb, int hook); +const struct tcphdr *nf_reject_ip6_tcphdr_get(struct sk_buff *oldskb, + struct tcphdr *otcph, + unsigned int *otcplen, int hook); +struct ipv6hdr *nf_reject_ip6hdr_put(struct sk_buff *nskb, + const struct sk_buff *oldskb, + __be16 protocol, int hoplimit); +void nf_reject_ip6_tcphdr_put(struct sk_buff *nskb, + const struct sk_buff *oldskb, + const struct tcphdr *oth, unsigned int otcplen); + #endif /* _IPV6_NF_REJECT_H */ diff --git a/net/ipv6/netfilter/nf_reject_ipv6.c b/net/ipv6/netfilter/nf_reject_ipv6.c index 20d9defc6c59..015eb8a80766 100644 --- a/net/ipv6/netfilter/nf_reject_ipv6.c +++ b/net/ipv6/netfilter/nf_reject_ipv6.c @@ -12,20 +12,131 @@ #include #include #include +#include + +const struct tcphdr *nf_reject_ip6_tcphdr_get(struct sk_buff *oldskb, + struct tcphdr *otcph, + unsigned int *otcplen, int hook) +{ + const struct ipv6hdr *oip6h = ipv6_hdr(oldskb); + u8 proto; + __be16 frag_off; + int tcphoff; + + proto = oip6h->nexthdr; + tcphoff = ipv6_skip_exthdr(oldskb, ((u8*)(oip6h+1) - oldskb->data), + &proto, &frag_off); + + if ((tcphoff < 0) || (tcphoff > oldskb->len)) { + pr_debug("Cannot get TCP header.\n"); + return NULL; + } + + *otcplen = oldskb->len - tcphoff; + + /* IP header checks: fragment, too short. */ + if (proto != IPPROTO_TCP || *otcplen < sizeof(struct tcphdr)) { + pr_debug("proto(%d) != IPPROTO_TCP or too short (len = %d)\n", + proto, *otcplen); + return NULL; + } + + otcph = skb_header_pointer(oldskb, tcphoff, sizeof(struct tcphdr), + otcph); + if (otcph == NULL) + return NULL; + + /* No RST for RST. */ + if (otcph->rst) { + pr_debug("RST is set\n"); + return NULL; + } + + /* Check checksum. */ + if (nf_ip6_checksum(oldskb, hook, tcphoff, IPPROTO_TCP)) { + pr_debug("TCP checksum is invalid\n"); + return NULL; + } + + return otcph; +} +EXPORT_SYMBOL_GPL(nf_reject_ip6_tcphdr_get); + +struct ipv6hdr *nf_reject_ip6hdr_put(struct sk_buff *nskb, + const struct sk_buff *oldskb, + __be16 protocol, int hoplimit) +{ + struct ipv6hdr *ip6h; + const struct ipv6hdr *oip6h = ipv6_hdr(oldskb); +#define DEFAULT_TOS_VALUE 0x0U + const __u8 tclass = DEFAULT_TOS_VALUE; + + skb_put(nskb, sizeof(struct ipv6hdr)); + skb_reset_network_header(nskb); + ip6h = ipv6_hdr(nskb); + ip6_flow_hdr(ip6h, tclass, 0); + ip6h->hop_limit = hoplimit; + ip6h->nexthdr = protocol; + ip6h->saddr = oip6h->daddr; + ip6h->daddr = oip6h->saddr; + + nskb->protocol = htons(ETH_P_IPV6); + + return ip6h; +} +EXPORT_SYMBOL_GPL(nf_reject_ip6hdr_put); + +void nf_reject_ip6_tcphdr_put(struct sk_buff *nskb, + const struct sk_buff *oldskb, + const struct tcphdr *oth, unsigned int otcplen) +{ + struct tcphdr *tcph; + int needs_ack; + + skb_reset_transport_header(nskb); + tcph = (struct tcphdr *)skb_put(nskb, sizeof(struct tcphdr)); + /* Truncate to length (no data) */ + tcph->doff = sizeof(struct tcphdr)/4; + tcph->source = oth->dest; + tcph->dest = oth->source; + + if (oth->ack) { + needs_ack = 0; + tcph->seq = oth->ack_seq; + tcph->ack_seq = 0; + } else { + needs_ack = 1; + tcph->ack_seq = htonl(ntohl(oth->seq) + oth->syn + oth->fin + + otcplen - (oth->doff<<2)); + tcph->seq = 0; + } + + /* Reset flags */ + ((u_int8_t *)tcph)[13] = 0; + tcph->rst = 1; + tcph->ack = needs_ack; + tcph->window = 0; + tcph->urg_ptr = 0; + tcph->check = 0; + + /* Adjust TCP checksum */ + tcph->check = csum_ipv6_magic(&ipv6_hdr(nskb)->saddr, + &ipv6_hdr(nskb)->daddr, + sizeof(struct tcphdr), IPPROTO_TCP, + csum_partial(tcph, + sizeof(struct tcphdr), 0)); +} +EXPORT_SYMBOL_GPL(nf_reject_ip6_tcphdr_put); void nf_send_reset6(struct net *net, struct sk_buff *oldskb, int hook) { struct sk_buff *nskb; - struct tcphdr otcph, *tcph; + struct tcphdr _otcph; + const struct tcphdr *otcph; unsigned int otcplen, hh_len; - int tcphoff, needs_ack; const struct ipv6hdr *oip6h = ipv6_hdr(oldskb); struct ipv6hdr *ip6h; -#define DEFAULT_TOS_VALUE 0x0U - const __u8 tclass = DEFAULT_TOS_VALUE; struct dst_entry *dst = NULL; - u8 proto; - __be16 frag_off; struct flowi6 fl6; if ((!(ipv6_addr_type(&oip6h->saddr) & IPV6_ADDR_UNICAST)) || @@ -34,45 +145,16 @@ void nf_send_reset6(struct net *net, struct sk_buff *oldskb, int hook) return; } - proto = oip6h->nexthdr; - tcphoff = ipv6_skip_exthdr(oldskb, ((u8*)(oip6h+1) - oldskb->data), &proto, &frag_off); - - if ((tcphoff < 0) || (tcphoff > oldskb->len)) { - pr_debug("Cannot get TCP header.\n"); + otcph = nf_reject_ip6_tcphdr_get(oldskb, &_otcph, &otcplen, hook); + if (!otcph) return; - } - - otcplen = oldskb->len - tcphoff; - - /* IP header checks: fragment, too short. */ - if (proto != IPPROTO_TCP || otcplen < sizeof(struct tcphdr)) { - pr_debug("proto(%d) != IPPROTO_TCP, " - "or too short. otcplen = %d\n", - proto, otcplen); - return; - } - - if (skb_copy_bits(oldskb, tcphoff, &otcph, sizeof(struct tcphdr))) - BUG(); - - /* No RST for RST. */ - if (otcph.rst) { - pr_debug("RST is set\n"); - return; - } - - /* Check checksum. */ - if (nf_ip6_checksum(oldskb, hook, tcphoff, IPPROTO_TCP)) { - pr_debug("TCP checksum is invalid\n"); - return; - } memset(&fl6, 0, sizeof(fl6)); fl6.flowi6_proto = IPPROTO_TCP; fl6.saddr = oip6h->daddr; fl6.daddr = oip6h->saddr; - fl6.fl6_sport = otcph.dest; - fl6.fl6_dport = otcph.source; + fl6.fl6_sport = otcph->dest; + fl6.fl6_dport = otcph->source; security_skb_classify_flow(oldskb, flowi6_to_flowi(&fl6)); dst = ip6_route_output(net, NULL, &fl6); if (dst == NULL || dst->error) { @@ -97,48 +179,9 @@ void nf_send_reset6(struct net *net, struct sk_buff *oldskb, int hook) skb_dst_set(nskb, dst); skb_reserve(nskb, hh_len + dst->header_len); - - skb_put(nskb, sizeof(struct ipv6hdr)); - skb_reset_network_header(nskb); - ip6h = ipv6_hdr(nskb); - ip6_flow_hdr(ip6h, tclass, 0); - ip6h->hop_limit = ip6_dst_hoplimit(dst); - ip6h->nexthdr = IPPROTO_TCP; - ip6h->saddr = oip6h->daddr; - ip6h->daddr = oip6h->saddr; - - skb_reset_transport_header(nskb); - tcph = (struct tcphdr *)skb_put(nskb, sizeof(struct tcphdr)); - /* Truncate to length (no data) */ - tcph->doff = sizeof(struct tcphdr)/4; - tcph->source = otcph.dest; - tcph->dest = otcph.source; - - if (otcph.ack) { - needs_ack = 0; - tcph->seq = otcph.ack_seq; - tcph->ack_seq = 0; - } else { - needs_ack = 1; - tcph->ack_seq = htonl(ntohl(otcph.seq) + otcph.syn + otcph.fin - + otcplen - (otcph.doff<<2)); - tcph->seq = 0; - } - - /* Reset flags */ - ((u_int8_t *)tcph)[13] = 0; - tcph->rst = 1; - tcph->ack = needs_ack; - tcph->window = 0; - tcph->urg_ptr = 0; - tcph->check = 0; - - /* Adjust TCP checksum */ - tcph->check = csum_ipv6_magic(&ipv6_hdr(nskb)->saddr, - &ipv6_hdr(nskb)->daddr, - sizeof(struct tcphdr), IPPROTO_TCP, - csum_partial(tcph, - sizeof(struct tcphdr), 0)); + ip6h = nf_reject_ip6hdr_put(nskb, oldskb, IPPROTO_TCP, + ip6_dst_hoplimit(dst)); + nf_reject_ip6_tcphdr_put(nskb, oldskb, otcph, otcplen); nf_ct_attach(nskb, oldskb);