From: Matthieu Baerts (NGI0) Date: Tue, 2 Jun 2026 12:14:18 +0000 (+1000) Subject: mptcp: add-addr: always drop other suboptions X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=bd34fa0257261b76964df1c98f44b3cb4ee14620;p=thirdparty%2Fkernel%2Flinux.git mptcp: add-addr: always drop other suboptions When an ADD_ADDR needs to be sent, it could be prepared if there is enough remaining space and even if the packet is not a pure ACK. But it would be dropped soon after. Indeed, in mptcp_pm_add_addr_signal(), there is enough space to fit a DSS of 20 octets and an ADD_ADDR echo containing an IPv4 address on 8 octets for example. In this case, the packet would be prepared, the MPTCP_ADD_ADDR_ECHO bit would be removed from pm->addr_signal, but the option would be silently dropped in mptcp_established_options_add_addr() not to override DSS info in the union from 'struct mptcp_out_options', and also because mptcp_write_options() will enforce mutually exclusion with DSS. Instead, don't even try to send an ADD_ADDR if it is not a pure ACK. Retry for each new packet until a pure-ACK is emitted. That's fine to do that, because each time an ADD_ADDR (echo) is scheduled, a pure ACK is queued. This also simplifies the code, and the skb checks can be done earlier, before the lock. Note: also, since commit 6d0060f600ad ("mptcp: Write MPTCP DSS headers to outgoing data packets"), opts->ahmac would not have been set to 0 when other suboptions were not dropped, and when sending an ADD_ADDR echo. That would have resulted in sending an ADD_ADDR using garbage info, where there was not enough space, instead of an echo one without the ADD_ADDR HMAC. Fixes: 1bff1e43a30e ("mptcp: optimize out option generation") Cc: stable@vger.kernel.org Signed-off-by: Matthieu Baerts (NGI0) Link: https://patch.msgid.link/20260602-net-mptcp-misc-fixes-7-1-rc7-v2-11-856831229976@kernel.org Signed-off-by: Jakub Kicinski --- diff --git a/net/mptcp/options.c b/net/mptcp/options.c index f9f587203c35..b3ea7854818f 100644 --- a/net/mptcp/options.c +++ b/net/mptcp/options.c @@ -665,7 +665,6 @@ static bool mptcp_established_options_add_addr(struct sock *sk, struct sk_buff * { struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk); struct mptcp_sock *msk = mptcp_sk(subflow->conn); - bool drop_other_suboptions = false; unsigned int opt_size = *size; struct mptcp_addr_info addr; bool echo; @@ -676,36 +675,20 @@ static bool mptcp_established_options_add_addr(struct sock *sk, struct sk_buff * */ if (!mptcp_pm_should_add_signal(msk) || (opts->suboptions & (OPTION_MPTCP_MPJ_ACK | OPTION_MPTCP_MPC_ACK)) || - !mptcp_pm_add_addr_signal(msk, skb, opt_size, remaining, &addr, - &echo, &drop_other_suboptions)) + !skb || !skb_is_tcp_pure_ack(skb) || + !mptcp_pm_add_addr_signal(msk, opt_size, remaining, &addr, &echo)) return false; - /* - * Later on, mptcp_write_options() will enforce mutually exclusion with - * DSS, bail out if such option is set and we can't drop it. - */ - if (drop_other_suboptions) - remaining += opt_size; - else if (opts->suboptions & OPTION_MPTCP_DSS) - return false; + remaining += opt_size; len = mptcp_add_addr_len(addr.family, echo, !!addr.port); if (remaining < len) return false; *size = len; - if (drop_other_suboptions) { - pr_debug("drop other suboptions\n"); - opts->suboptions = 0; - - /* note that e.g. DSS could have written into the memory - * aliased by ahmac, we must reset the field here - * to avoid appending the hmac even for ADD_ADDR echo - * options - */ - opts->ahmac = 0; - *size -= opt_size; - } + pr_debug("drop other suboptions\n"); + opts->suboptions = 0; + *size -= opt_size; opts->addr = addr; opts->suboptions |= OPTION_MPTCP_ADD_ADDR; if (!echo) { @@ -715,6 +698,7 @@ static bool mptcp_established_options_add_addr(struct sock *sk, struct sk_buff * &opts->addr); } else { MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_ECHOADDTX); + opts->ahmac = 0; } pr_debug("addr_id=%d, ahmac=%llu, echo=%d, port=%d\n", opts->addr.id, opts->ahmac, echo, ntohs(opts->addr.port)); diff --git a/net/mptcp/pm.c b/net/mptcp/pm.c index 3e770c7407e1..470501470fe5 100644 --- a/net/mptcp/pm.c +++ b/net/mptcp/pm.c @@ -887,10 +887,9 @@ void mptcp_pm_mp_fail_received(struct sock *sk, u64 fail_seq) } } -bool mptcp_pm_add_addr_signal(struct mptcp_sock *msk, const struct sk_buff *skb, - unsigned int opt_size, unsigned int remaining, - struct mptcp_addr_info *addr, bool *echo, - bool *drop_other_suboptions) +bool mptcp_pm_add_addr_signal(struct mptcp_sock *msk, unsigned int opt_size, + unsigned int remaining, + struct mptcp_addr_info *addr, bool *echo) { bool skip_add_addr = false; int ret = false; @@ -908,10 +907,7 @@ bool mptcp_pm_add_addr_signal(struct mptcp_sock *msk, const struct sk_buff *skb, * plain dup-ack from TCP perspective. The other MPTCP-relevant info, * if any, will be carried by the 'original' TCP ack */ - if (skb && skb_is_tcp_pure_ack(skb)) { - remaining += opt_size; - *drop_other_suboptions = true; - } + remaining += opt_size; *echo = mptcp_pm_should_add_signal_echo(msk); if (*echo) { @@ -929,9 +925,6 @@ bool mptcp_pm_add_addr_signal(struct mptcp_sock *msk, const struct sk_buff *skb, if (remaining < mptcp_add_addr_len(family, *echo, port)) { struct net *net = sock_net((struct sock *)msk); - if (!*drop_other_suboptions) - goto out_unlock; - if (*echo) { MPTCP_INC_STATS(net, MPTCP_MIB_ECHOADDTXDROP); } else { diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h index e4f5aba24da7..b93b878478d2 100644 --- a/net/mptcp/protocol.h +++ b/net/mptcp/protocol.h @@ -1229,10 +1229,9 @@ static inline int mptcp_rm_addr_len(const struct mptcp_rm_list *rm_list) return TCPOLEN_MPTCP_RM_ADDR_BASE + roundup(rm_list->nr - 1, 4) + 1; } -bool mptcp_pm_add_addr_signal(struct mptcp_sock *msk, const struct sk_buff *skb, - unsigned int opt_size, unsigned int remaining, - struct mptcp_addr_info *addr, bool *echo, - bool *drop_other_suboptions); +bool mptcp_pm_add_addr_signal(struct mptcp_sock *msk, unsigned int opt_size, + unsigned int remaining, + struct mptcp_addr_info *addr, bool *echo); bool mptcp_pm_rm_addr_signal(struct mptcp_sock *msk, unsigned int remaining, struct mptcp_rm_list *rm_list); int mptcp_pm_get_local_id(struct mptcp_sock *msk, struct sock_common *skc);