From c65e820c85fe9777a83ec8c5350803782d42368b Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Sun, 24 May 2020 11:00:02 -0700 Subject: [PATCH] tcp: allow traceroute -Mtcp for unpriv users MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit Unpriv users can use traceroute over plain UDP sockets, but not TCP ones. $ traceroute -Mtcp 8.8.8.8 You do not have enough privileges to use this traceroute method. $ traceroute -n -Mudp 8.8.8.8 traceroute to 8.8.8.8 (8.8.8.8), 30 hops max, 60 byte packets 1 192.168.86.1 3.631 ms 3.512 ms 3.405 ms 2 10.1.10.1 4.183 ms 4.125 ms 4.072 ms 3 96.120.88.125 20.621 ms 19.462 ms 20.553 ms 4 96.110.177.65 24.271 ms 25.351 ms 25.250 ms 5 69.139.199.197 44.492 ms 43.075 ms 44.346 ms 6 68.86.143.93 27.969 ms 25.184 ms 25.092 ms 7 96.112.146.18 25.323 ms 96.112.146.22 25.583 ms 96.112.146.26 24.502 ms 8 72.14.239.204 24.405 ms 74.125.37.224 16.326 ms 17.194 ms 9 209.85.251.9 18.154 ms 209.85.247.55 14.449 ms 209.85.251.9 26.296 ms^C We can easily support traceroute over TCP, by queueing an error message into socket error queue. Note that applications need to set IP_RECVERR/IPV6_RECVERR option to enable this feature, and that the error message is only queued while in SYN_SNT state. socket(AF_INET6, SOCK_STREAM, IPPROTO_IP) = 3 setsockopt(3, SOL_IPV6, IPV6_RECVERR, [1], 4) = 0 setsockopt(3, SOL_SOCKET, SO_TIMESTAMP_OLD, [1], 4) = 0 setsockopt(3, SOL_IPV6, IPV6_UNICAST_HOPS, [5], 4) = 0 connect(3, {sa_family=AF_INET6, sin6_port=htons(8787), sin6_flowinfo=htonl(0), inet_pton(AF_INET6, "2002:a05:6608:297::", &sin6_addr), sin6_scope_id=0}, 28) = -1 EHOSTUNREACH (No route to host) recvmsg(3, {msg_name={sa_family=AF_INET6, sin6_port=htons(8787), sin6_flowinfo=htonl(0), inet_pton(AF_INET6, "2002:a05:6608:297::", &sin6_addr), sin6_scope_id=0}, msg_namelen=1024->28, msg_iov=[{iov_base="`\r\337\320\0004\6\1&\7\370\260\200\231\16\27\0\0\0\0\0\0\0\0 \2\n\5f\10\2\227"..., iov_len=1024}], msg_iovlen=1, msg_control=[{cmsg_len=32, cmsg_level=SOL_SOCKET, cmsg_type=SO_TIMESTAMP_OLD, cmsg_data={tv_sec=1590340680, tv_usec=272424}}, {cmsg_len=60, cmsg_level=SOL_IPV6, cmsg_type=IPV6_RECVERR}], msg_controllen=96, msg_flags=MSG_ERRQUEUE}, MSG_ERRQUEUE) = 144 Suggested-by: Maciej Żenczykowski Cc: Willem de Bruijn Reviewed-by: Maciej Żenczykowski Signed-off-by: David S. Miller --- net/ipv4/tcp_ipv4.c | 2 ++ net/ipv6/tcp_ipv6.c | 2 ++ 2 files changed, 4 insertions(+) diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c index 6c05f1ceb538c..900c6d154cbcf 100644 --- a/net/ipv4/tcp_ipv4.c +++ b/net/ipv4/tcp_ipv4.c @@ -573,6 +573,8 @@ int tcp_v4_err(struct sk_buff *icmp_skb, u32 info) if (fastopen && !fastopen->sk) break; + ip_icmp_error(sk, skb, err, th->dest, info, (u8 *)th); + if (!sock_owned_by_user(sk)) { sk->sk_err = err; diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c index 413b3425ac66b..01a6f5111a77b 100644 --- a/net/ipv6/tcp_ipv6.c +++ b/net/ipv6/tcp_ipv6.c @@ -463,6 +463,8 @@ static int tcp_v6_err(struct sk_buff *skb, struct inet6_skb_parm *opt, if (fastopen && !fastopen->sk) break; + ipv6_icmp_error(sk, skb, err, th->dest, ntohl(info), (u8 *)th); + if (!sock_owned_by_user(sk)) { sk->sk_err = err; sk->sk_error_report(sk); /* Wake people up to see the error (see connect in sock.c) */ -- 2.39.5