Subject: Re: [RFC PATCH 2/5] sctp: Add ip option support

From: Marcelo Ricardo Leitner <[email-masked]>
Date: Tue, 31 Oct 2017 15:06:06 -0200

Hello,

On Tue, Oct 17, 2017 at 02:58:06PM +0100, Richard Haines wrote:
> Add ip option support to allow LSM security modules to utilise CIPSO/IPv4
> and CALIPSO/IPv6 services.
> 
> Signed-off-by: Richard Haines <[email-masked]>
> ---
>  include/net/sctp/structs.h |  2 ++
>  net/sctp/chunk.c           |  7 ++++---
>  net/sctp/ipv6.c            | 37 ++++++++++++++++++++++++++++++-------
>  net/sctp/output.c          |  3 ++-
>  net/sctp/protocol.c        | 36 ++++++++++++++++++++++++++++++++++++
>  net/sctp/socket.c          |  5 ++++-
>  6 files changed, 78 insertions(+), 12 deletions(-)
> 
> diff --git a/include/net/sctp/structs.h b/include/net/sctp/structs.h
> index 5ab29af..7767577 100644
> --- a/include/net/sctp/structs.h
> +++ b/include/net/sctp/structs.h
> @@ -461,6 +461,7 @@ struct sctp_af {
>  	void		(*ecn_capable)(struct sock *sk);
>  	__u16		net_header_len;
>  	int		sockaddr_len;
> +	int		(*ip_options_len)(struct sock *sk);
>  	sa_family_t	sa_family;
>  	struct list_head list;
>  };
> @@ -485,6 +486,7 @@ struct sctp_pf {
>  	int (*addr_to_user)(struct sctp_sock *sk, union sctp_addr *addr);
>  	void (*to_sk_saddr)(union sctp_addr *, struct sock *sk);
>  	void (*to_sk_daddr)(union sctp_addr *, struct sock *sk);
> +	void (*copy_ip_options)(struct sock *sk, struct sock *newsk);
>  	struct sctp_af *af;
>  };
>  
> diff --git a/net/sctp/chunk.c b/net/sctp/chunk.c
> index 1323d41..e49e240 100644
> --- a/net/sctp/chunk.c
> +++ b/net/sctp/chunk.c
> @@ -153,7 +153,6 @@ static void sctp_datamsg_assign(struct sctp_datamsg *msg, struct sctp_chunk *chu
>  	chunk->msg = msg;
>  }
>  
> -
>  /* A data chunk can have a maximum payload of (2^16 - 20).  Break
>   * down any such message into smaller chunks.  Opportunistically, fragment
>   * the chunks down to the current MTU constraints.  We may get refragmented
> @@ -190,7 +189,10 @@ struct sctp_datamsg *sctp_datamsg_from_user(struct sctp_association *asoc,
>  	 */
>  	max_data = asoc->pathmtu -
>  		   sctp_sk(asoc->base.sk)->pf->af->net_header_len -
                                        ^^^^^^^^
> -		   sizeof(struct sctphdr) - sizeof(struct sctp_data_chunk);
> +		   sizeof(struct sctphdr) - sizeof(struct sctp_data_chunk) -
> +		   sctp_sk(asoc->base.sk)->pf->af->
                                        ^^^^^^^^
> +		   ip_options_len(asoc->base.sk);

Please add a var for sctp_sk(asoc->base.sk)->pf->af. That should also
help to not break the dereferencing into multiple lines.

> +
>  	max_data = SCTP_TRUNC4(max_data);
>  
>  	/* If the the peer requested that we authenticate DATA chunks
> @@ -210,7 +212,6 @@ struct sctp_datamsg *sctp_datamsg_from_user(struct sctp_association *asoc,
>  
>  	/* Set first_len and then account for possible bundles on first frag */
>  	first_len = max_data;
> -
>  	/* Check to see if we have a pending SACK and try to let it be bundled
>  	 * with this message.  Do this if we don't have any data queued already.
>  	 * To check that, look at out_qlen and retransmit list.
> diff --git a/net/sctp/ipv6.c b/net/sctp/ipv6.c
> index a4b6ffb..49c9011 100644
> --- a/net/sctp/ipv6.c
> +++ b/net/sctp/ipv6.c
> @@ -423,6 +423,33 @@ static void sctp_v6_copy_addrlist(struct list_head *addrlist,
>  	rcu_read_unlock();
>  }
>  
> +/* Copy over any ip options */
> +static void sctp_v6_copy_ip_options(struct sock *sk, struct sock *newsk)
> +{
> +	struct ipv6_pinfo *newnp, *np = inet6_sk(sk);
> +	struct ipv6_txoptions *opt;
> +
> +	newnp = inet6_sk(newsk);
> +
> +	rcu_read_lock();
> +	opt = rcu_dereference(np->opt);
> +	if (opt)
> +		opt = ipv6_dup_options(newsk, opt);
> +	RCU_INIT_POINTER(newnp->opt, opt);
> +	rcu_read_unlock();
> +}
> +
> +/* Account for the IP options */
> +static int sctp_v6_ip_options_len(struct sock *sk)
> +{
> +	struct ipv6_pinfo *inet6 = inet6_sk(sk);
> +
> +	if (inet6->opt)
> +		return inet6->opt->opt_flen + inet6->opt->opt_nflen;

Seems we need RCU protection here.
And please add a var for inet6->opt.

> +	else
> +		return 0;
> +}
> +
>  /* Initialize a sockaddr_storage from in incoming skb. */
>  static void sctp_v6_from_skb(union sctp_addr *addr, struct sk_buff *skb,
>  			     int is_saddr)
> @@ -662,7 +689,6 @@ static struct sock *sctp_v6_create_accept_sk(struct sock *sk,
>  	struct sock *newsk;
>  	struct ipv6_pinfo *newnp, *np = inet6_sk(sk);
>  	struct sctp6_sock *newsctp6sk;
> -	struct ipv6_txoptions *opt;
>  
>  	newsk = sk_alloc(sock_net(sk), PF_INET6, GFP_KERNEL, sk->sk_prot, kern);
>  	if (!newsk)
> @@ -685,12 +711,7 @@ static struct sock *sctp_v6_create_accept_sk(struct sock *sk,
>  	newnp->ipv6_ac_list = NULL;
>  	newnp->ipv6_fl_list = NULL;
>  
> -	rcu_read_lock();
> -	opt = rcu_dereference(np->opt);
> -	if (opt)
> -		opt = ipv6_dup_options(newsk, opt);
> -	RCU_INIT_POINTER(newnp->opt, opt);
> -	rcu_read_unlock();
> +	sctp_v6_copy_ip_options(sk, newsk);
>  
>  	/* Initialize sk's sport, dport, rcv_saddr and daddr for getsockname()
>  	 * and getpeername().
> @@ -1033,6 +1054,7 @@ static struct sctp_af sctp_af_inet6 = {
>  	.ecn_capable	   = sctp_v6_ecn_capable,
>  	.net_header_len	   = sizeof(struct ipv6hdr),
>  	.sockaddr_len	   = sizeof(struct sockaddr_in6),
> +	.ip_options_len	   = sctp_v6_ip_options_len,
>  #ifdef CONFIG_COMPAT
>  	.compat_setsockopt = compat_ipv6_setsockopt,
>  	.compat_getsockopt = compat_ipv6_getsockopt,
> @@ -1051,6 +1073,7 @@ static struct sctp_pf sctp_pf_inet6 = {
>  	.addr_to_user  = sctp_v6_addr_to_user,
>  	.to_sk_saddr   = sctp_v6_to_sk_saddr,
>  	.to_sk_daddr   = sctp_v6_to_sk_daddr,
> +	.copy_ip_options = sctp_v6_copy_ip_options,
>  	.af            = &sctp_af_inet6,
>  };
>  
> diff --git a/net/sctp/output.c b/net/sctp/output.c
> index 9d85049..85bcd5b 100644
> --- a/net/sctp/output.c
> +++ b/net/sctp/output.c
> @@ -151,7 +151,8 @@ void sctp_packet_init(struct sctp_packet *packet,
>  	INIT_LIST_HEAD(&packet->chunk_list);
>  	if (asoc) {
>  		struct sctp_sock *sp = sctp_sk(asoc->base.sk);
> -		overhead = sp->pf->af->net_header_len;
> +		overhead = sp->pf->af->net_header_len +
> +			   sp->pf->af->ip_options_len(asoc->base.sk);

Here you may also add a var for sp->pf->af.

>  	} else {
>  		overhead = sizeof(struct ipv6hdr);
>  	}
> diff --git a/net/sctp/protocol.c b/net/sctp/protocol.c
> index 989a900..a9e54ac 100644
> --- a/net/sctp/protocol.c
> +++ b/net/sctp/protocol.c
> @@ -237,6 +237,38 @@ int sctp_copy_local_addr_list(struct net *net, struct sctp_bind_addr *bp,
>  	return error;
>  }
>  
> +/* Copy over any ip options */
> +static void sctp_v4_copy_ip_options(struct sock *sk, struct sock *newsk)
> +{
> +	struct inet_sock *newinet, *inet = inet_sk(sk);
> +	struct ip_options_rcu *inet_opt, *newopt = NULL;
> +
> +	newinet = inet_sk(newsk);
> +
> +	rcu_read_lock();
> +	inet_opt = rcu_dereference(inet->inet_opt);
> +	if (inet_opt) {
> +		newopt = sock_kmalloc(newsk, sizeof(*inet_opt) +
> +				      inet_opt->opt.optlen, GFP_ATOMIC);
> +		if (newopt)
> +			memcpy(newopt, inet_opt, sizeof(*inet_opt) +
> +			       inet_opt->opt.optlen);
> +	}
> +	RCU_INIT_POINTER(newinet->inet_opt, newopt);
> +	rcu_read_unlock();
> +}
> +
> +/* Account for the IP options */
> +static int sctp_v4_ip_options_len(struct sock *sk)
> +{
> +	struct inet_sock *inet = inet_sk(sk);
> +
> +	if (inet->inet_opt)
> +		return inet->inet_opt->opt.optlen;
> +	else
> +		return 0;
> +}
> +
>  /* Initialize a sctp_addr from in incoming skb.  */
>  static void sctp_v4_from_skb(union sctp_addr *addr, struct sk_buff *skb,
>  			     int is_saddr)
> @@ -590,6 +622,8 @@ static struct sock *sctp_v4_create_accept_sk(struct sock *sk,
>  	sctp_copy_sock(newsk, sk, asoc);
>  	sock_reset_flag(newsk, SOCK_ZAPPED);
>  
> +	sctp_v4_copy_ip_options(sk, newsk);
> +
>  	newinet = inet_sk(newsk);
>  
>  	newinet->inet_daddr = asoc->peer.primary_addr.v4.sin_addr.s_addr;
> @@ -1008,6 +1042,7 @@ static struct sctp_pf sctp_pf_inet = {
>  	.addr_to_user  = sctp_v4_addr_to_user,
>  	.to_sk_saddr   = sctp_v4_to_sk_saddr,
>  	.to_sk_daddr   = sctp_v4_to_sk_daddr,
> +	.copy_ip_options = sctp_v4_copy_ip_options,
>  	.af            = &sctp_af_inet
>  };
>  
> @@ -1092,6 +1127,7 @@ static struct sctp_af sctp_af_inet = {
>  	.ecn_capable	   = sctp_v4_ecn_capable,
>  	.net_header_len	   = sizeof(struct iphdr),
>  	.sockaddr_len	   = sizeof(struct sockaddr_in),
> +	.ip_options_len	   = sctp_v4_ip_options_len,
>  #ifdef CONFIG_COMPAT
>  	.compat_setsockopt = compat_ip_setsockopt,
>  	.compat_getsockopt = compat_ip_getsockopt,
> diff --git a/net/sctp/socket.c b/net/sctp/socket.c
> index 8d76086..70355a0 100644
> --- a/net/sctp/socket.c
> +++ b/net/sctp/socket.c
> @@ -3124,6 +3124,7 @@ static int sctp_setsockopt_maxseg(struct sock *sk, char __user *optval, unsigned
>  	if (asoc) {
>  		if (val == 0) {
>  			val = asoc->pathmtu;
> +			val -= sp->pf->af->ip_options_len(asoc->base.sk);
>  			val -= sp->pf->af->net_header_len;

Also here. May even be inside the if() block.

Thanks

>  			val -= sizeof(struct sctphdr) +
>  					sizeof(struct sctp_data_chunk);
> @@ -4917,9 +4918,11 @@ int sctp_do_peeloff(struct sock *sk, sctp_assoc_t id, struct socket **sockp)
>  	sctp_copy_sock(sock->sk, sk, asoc);
>  
>  	/* Make peeled-off sockets more like 1-1 accepted sockets.
> -	 * Set the daddr and initialize id to something more random
> +	 * Set the daddr and initialize id to something more random and also
> +	 * copy over any ip options.
>  	 */
>  	sp->pf->to_sk_daddr(&asoc->peer.primary_addr, sk);
> +	sp->pf->copy_ip_options(sk, sock->sk);
>  
>  	/* Populate the fields of the newsk from the oldsk and migrate the
>  	 * asoc to the newsk.
> -- 
> 2.13.6
> 
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