linux-yocto - Yocto Linux Embedded kernel

Age	Commit message (Expand)	Author
2017-08-08	drm: Nuke drm_atomic_helper_connector_dpms	Daniel Vetter
2017-04-06	drm: convert drivers to use drm_of_find_panel_or_bridge	Rob Herring
2017-03-10	drm: mxsfb: Fix crash when provided invalid DT bindings	Marek Vasut
2016-12-06	drm: Add new driver for MXSFB controller	Marek Vasut

// SPDX-License-Identifier: GPL-2.0-only /* * This is a module which is used for setting the MSS option in TCP packets. * * Copyright (C) 2000 Marc Boucher <marc@mbsi.ca> * Copyright (C) 2007 Patrick McHardy <kaber@trash.net> */ #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt #include <linux/module.h> #include <linux/skbuff.h> #include <linux/ip.h> #include <linux/gfp.h> #include <linux/ipv6.h> #include <linux/tcp.h> #include <net/dst.h> #include <net/flow.h> #include <net/ipv6.h> #include <net/route.h> #include <net/tcp.h> #include <linux/netfilter_ipv4/ip_tables.h> #include <linux/netfilter_ipv6/ip6_tables.h> #include <linux/netfilter/x_tables.h> #include <linux/netfilter/xt_tcpudp.h> #include <linux/netfilter/xt_TCPMSS.h> MODULE_LICENSE("GPL"); MODULE_AUTHOR("Marc Boucher <marc@mbsi.ca>"); MODULE_DESCRIPTION("Xtables: TCP Maximum Segment Size (MSS) adjustment"); MODULE_ALIAS("ipt_TCPMSS"); MODULE_ALIAS("ip6t_TCPMSS"); static inline unsigned int optlen(const u_int8_t *opt, unsigned int offset) { /* Beware zero-length options: make finite progress */ if (opt[offset] <= TCPOPT_NOP || opt[offset+1] == 0) return 1; else return opt[offset+1]; } static u_int32_t tcpmss_reverse_mtu(struct net *net, const struct sk_buff *skb, unsigned int family) { struct flowi fl; struct rtable *rt = NULL; u_int32_t mtu = ~0U; if (family == PF_INET) { struct flowi4 *fl4 = &fl.u.ip4; memset(fl4, 0, sizeof(*fl4)); fl4->daddr = ip_hdr(skb)->saddr; } else { struct flowi6 *fl6 = &fl.u.ip6; memset(fl6, 0, sizeof(*fl6)); fl6->daddr = ipv6_hdr(skb)->saddr; } nf_route(net, (struct dst_entry **)&rt, &fl, false, family); if (rt != NULL) { mtu = dst_mtu(&rt->dst); dst_release(&rt->dst); } return mtu; } static int tcpmss_mangle_packet(struct sk_buff *skb, const struct xt_action_param *par, unsigned int family, unsigned int tcphoff, unsigned int minlen) { const struct xt_tcpmss_info *info = par->targinfo; struct tcphdr *tcph; int len, tcp_hdrlen; unsigned int i; __be16 oldval; u16 newmss; u8 *opt; /* This is a fragment, no TCP header is available */ if (par->fragoff != 0) return 0; if (!skb_make_writable(skb, skb->len)) return -1; len = skb->len - tcphoff; if (len < (int)sizeof(struct tcphdr)) return -1; tcph = (struct tcphdr *)(skb_network_header(skb) + tcphoff); tcp_hdrlen = tcph->doff * 4; if (len < tcp_hdrlen || tcp_hdrlen < sizeof(struct tcphdr)) return -1; if (info->mss == XT_TCPMSS_CLAMP_PMTU) { struct net *net = xt_net(par); unsigned int in_mtu = tcpmss_reverse_mtu(net, skb, family); unsigned int min_mtu = min(dst_mtu(skb_dst(skb)), in_mtu); if (min_mtu <= minlen) { net_err_ratelimited("unknown or invalid path-MTU (%u)\n", min_mtu); return -1; } newmss = min_mtu - minlen; } else newmss = info->mss; opt = (u_int8_t *)tcph; for (i = sizeof(struct tcphdr); i <= tcp_hdrlen - TCPOLEN_MSS; i += optlen(opt, i)) { if (opt[i] == TCPOPT_MSS && opt[i+1] == TCPOLEN_MSS) { u_int16_t oldmss; oldmss = (opt[i+2] << 8) | opt[i+3]; /* Never increase MSS, even when setting it, as * doing so results in problems for hosts that rely * on MSS being set correctly. */ if (oldmss <= newmss) return 0; opt[i+2] = (newmss & 0xff00) >> 8; opt[i+3] = newmss & 0x00ff; inet_proto_csum_replace2(&tcph->check, skb, htons(oldmss), htons(newmss), false); return 0; } } /* There is data after the header so the option can't be added * without moving it, and doing so may make the SYN packet * itself too large. Accept the packet unmodified instead. */ if (len > tcp_hdrlen) return 0; /* tcph->doff has 4 bits, do not wrap it to 0 */ if (tcp_hdrlen >= 15 * 4) return 0; /* * MSS Option not found ?! add it.. */ if (skb_tailroom(skb) < TCPOLEN_MSS) { if (pskb_expand_head(skb, 0, TCPOLEN_MSS - skb_tailroom(skb), GFP_ATOMIC)) return -1; tcph = (struct tcphdr *)(skb_network_header(skb) + tcphoff); } skb_put(skb, TCPOLEN_MSS); /* * IPv4: RFC 1122 states "If an MSS option is not received at * connection setup, TCP MUST assume a default send MSS of 536". * IPv6: RFC 2460 states IPv6 has a minimum MTU of 1280 and a minimum * length IPv6 header of 60, ergo the default MSS value is 1220 * Since no MSS was provided, we must use the default values */ if (xt_family(par) == NFPROTO_IPV4) newmss = min(newmss, (u16)536); else newmss = min(newmss, (u16)1220); opt = (u_int8_t *)tcph + sizeof(struct tcphdr); memmove(opt + TCPOLEN_MSS, opt, len - sizeof(struct tcphdr)); inet_proto_csum_replace2(&tcph->check, skb, htons(len), htons(len + TCPOLEN_MSS), true); opt[0] = TCPOPT_MSS; opt[1] = TCPOLEN_MSS; opt[2] = (newmss & 0xff00) >> 8; opt[3] = newmss & 0x00ff; inet_proto_csum_replace4(&tcph->check, skb, 0, *((__be32 *)opt), false); oldval = ((__be16 *)tcph)[6]; tcph->doff += TCPOLEN_MSS/4; inet_proto_csum_replace2(&tcph->check, skb, oldval, ((__be16 *)tcph)[6], false); return TCPOLEN_MSS; } static unsigned int tcpmss_tg4(struct sk_buff *skb, const struct xt_action_param *par) { struct iphdr *iph = ip_hdr(skb); __be16 newlen; int ret; ret = tcpmss_mangle_packet(skb, par, PF_INET, iph->ihl * 4, sizeof(*iph) + sizeof(struct tcphdr)); if (ret < 0) return NF_DROP; if (ret > 0) { iph = ip_hdr(skb); newlen = htons(ntohs(iph->tot_len) + ret); csum_replace2(&iph->check, iph->tot_len, newlen); iph->tot_len = newlen; } return XT_CONTINUE; } #if IS_ENABLED(CONFIG_IP6_NF_IPTABLES) static unsigned int tcpmss_tg6(struct sk_buff *skb, const struct xt_action_param *par) { struct ipv6hdr *ipv6h = ipv6_hdr(skb); u8 nexthdr; __be16 frag_off, oldlen, newlen; int tcphoff; int ret; nexthdr = ipv6h->nexthdr; tcphoff = ipv6_skip_exthdr(skb, sizeof(*ipv6h), &nexthdr, &frag_off); if (tcphoff < 0) return NF_DROP; ret = tcpmss_mangle_packet(skb, par, PF_INET6, tcphoff, sizeof(*ipv6h) + sizeof(struct tcphdr)); if (ret < 0) return NF_DROP; if (ret > 0) { ipv6h = ipv6_hdr(skb); oldlen = ipv6h->payload_len; newlen = htons(ntohs(oldlen) + ret); if (skb->ip_summed == CHECKSUM_COMPLETE) skb->csum = csum_add(csum_sub(skb->csum, oldlen), newlen); ipv6h->payload_len = newlen; } return XT_CONTINUE; } #endif /* Must specify -p tcp --syn */ static inline bool find_syn_match(const struct xt_entry_match *m) { const struct xt_tcp *tcpinfo = (const struct xt_tcp *)m->data; if (strcmp(m->u.kernel.match->name, "tcp") == 0 && tcpinfo->flg_cmp & TCPHDR_SYN && !(tcpinfo->invflags & XT_TCP_INV_FLAGS)) return true; return false; } static int tcpmss_tg4_check(const struct xt_tgchk_param *par) { const struct xt_tcpmss_info *info = par->targinfo; const struct ipt_entry *e = par->entryinfo; const struct xt_entry_match *ematch; if (info->mss == XT_TCPMSS_CLAMP_PMTU && (par->hook_mask & ~((1 << NF_INET_FORWARD) | (1 << NF_INET_LOCAL_OUT) | (1 << NF_INET_POST_ROUTING))) != 0) { pr_info_ratelimited("path-MTU clamping only supported in FORWARD, OUTPUT and POSTROUTING hooks\n"); return -EINVAL; } if (par->nft_compat) return 0; xt_ematch_foreach(ematch, e) if (find_syn_match(ematch)) return 0; pr_info_ratelimited("Only works on TCP SYN packets\n"); return -EINVAL; } #if IS_ENABLED(CONFIG_IP6_NF_IPTABLES) static int tcpmss_tg6_check(const struct xt_tgchk_param *par) { const struct xt_tcpmss_info *info = par->targinfo; const struct ip6t_entry *e = par->entryinfo; const struct xt_entry_match *ematch; if (info->mss == XT_TCPMSS_CLAMP_PMTU && (par->hook_mask & ~((1 << NF_INET_FORWARD) | (1 << NF_INET_LOCAL_OUT) | (1 << NF_INET_POST_ROUTING))) != 0) { pr_info_ratelimited("path-MTU clamping only supported in FORWARD, OUTPUT and POSTROUTING hooks\n"); return -EINVAL; } if (par->nft_compat) return 0; xt_ematch_foreach(ematch, e) if (find_syn_match(ematch)) return 0; pr_info_ratelimited("Only works on TCP SYN packets\n"); return -EINVAL; } #endif static struct xt_target tcpmss_tg_reg[] __read_mostly = { { .family = NFPROTO_IPV4, .name = "TCPMSS", .checkentry = tcpmss_tg4_check, .target = tcpmss_tg4, .targetsize = sizeof(struct xt_tcpmss_info), .proto = IPPROTO_TCP, .me = THIS_MODULE, }, #if IS_ENABLED(CONFIG_IP6_NF_IPTABLES) { .family = NFPROTO_IPV6, .name = "TCPMSS", .checkentry = tcpmss_tg6_check, .target = tcpmss_tg6, .targetsize = sizeof(struct xt_tcpmss_info), .proto = IPPROTO_TCP, .me = THIS_MODULE, }, #endif }; static int __init tcpmss_tg_init(void) { return xt_register_targets(tcpmss_tg_reg, ARRAY_SIZE(tcpmss_tg_reg)); } static void __exit tcpmss_tg_exit(void) { xt_unregister_targets(tcpmss_tg_reg, ARRAY_SIZE(tcpmss_tg_reg)); } module_init(tcpmss_tg_init); module_exit(tcpmss_tg_exit);