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Tue, 20 Oct 2026 08:07:35 -0700 (PDT) Received: from localhost ([153.61.198.248]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2ea3b4ae277sm277345ad.76.2026.10.20.08.07.31 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 20 Oct 2026 08:07:32 -0700 (PDT) Content-Type: text/plain; charset=UTF-8 Date: Tue, 20 Oct 2026 15:07:31 +0000 Message-Id: Cc: , , , , , , , , , , , , , , , , , , , , Subject: Re: [PATCH bpf-next 0/8] bpf: Expand ksock send-path support From: "Alexei Starovoitov" To: "Mahe Tardy" , In-Reply-To: <20261020102512.518479-1-mahe.tardy@gmail.com> References: <20261020102512.518479-1-mahe.tardy@gmail.com> X-Mailer: mkdraft (claude review draft; edit before sending) Content-Transfer-Encoding: 8bit X-Mailing-List: bpf@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 On Tue, Oct 20, 2026 at 03:25 AM Mahe Tardy wrote: > * allow bpf_ksock_connect() to be called in the send path > * add bpf_ksock_sendto() kfunc to complement to bpf_ksock_send() > > This is useful when using ksock to reply to differents peers while > reusing the same UDP socket and generally works toward the goal of ksock > to support the basic socket operations. can we drop connect from LSM progs and patches 1-5 altogether ? bpf_ksock_sendto() alone replies to different peers on one socket. connect + send from LSM progs can't do that reliably. The socket is shared through the kptr and sleepable progs run concurrently. Between bpf_ksock_connect(A) and bpf_ksock_send() on one CPU, another CPU does bpf_ksock_connect(B) and the datagram for A goes to B. Without connect there, acquire/release in socket_sendmsg has no user: nothing can be done with that reference. bpf_ksock_sendto() is in ksock_kfunc_btf_ids, so the current filter rejects it in socket_sendmsg already. Then no need for bpf_ksock_send_id, bpf_ksock_sendto_id, bpf_ksock_connect_id, bpf_lsm_socket_connect_id and the cycle comment. Selftests are left out below. Patch 8 stays as is, patch 7 stays without the socket_connect hunk. Something like this (compile tested only): diff --git a/net/core/bpf_ksock.c b/net/core/bpf_ksock.c index 48a2e23..48757dc 100644 --- a/net/core/bpf_ksock.c +++ b/net/core/bpf_ksock.c @@ -37,6 +37,25 @@ static void ksock_release_work_fn(struct work_struct *work) kfree(ks); } +static int bpf_ksock_addr_to_sockaddr(const union bpf_ksock_addr *addr, + u32 addr_sz, struct sockaddr_storage *sa) +{ + if (!addr || addr_sz != sizeof(*addr)) + return -EINVAL; + + /* Kfunc memory arguments may be unaligned. */ + memcpy(sa, addr, sizeof(*addr)); + + switch (sa->ss_family) { + case AF_INET: + return sizeof(struct sockaddr_in); + case AF_INET6: + return sizeof(struct sockaddr_in6); + default: + return -EAFNOSUPPORT; + } +} + __bpf_kfunc_start_defs(); /** @@ -155,22 +174,9 @@ __bpf_kfunc int bpf_ksock_connect(struct bpf_ksock *ks, struct sockaddr_storage sa; int addrlen; - if (!addr || addr__sz != sizeof(*addr)) - return -EINVAL; - - /* Kfunc memory arguments may be unaligned. */ - memcpy(&sa, addr, sizeof(*addr)); - - switch (sa.ss_family) { - case AF_INET: - addrlen = sizeof(struct sockaddr_in); - break; - case AF_INET6: - addrlen = sizeof(struct sockaddr_in6); - break; - default: - return -EAFNOSUPPORT; - } + addrlen = bpf_ksock_addr_to_sockaddr(addr, addr__sz, &sa); + if (addrlen < 0) + return addrlen; return connect_socket(ks->sock, &sa, addrlen, 0); } @@ -212,19 +218,25 @@ __bpf_kfunc void bpf_ksock_release_dtor(void *ks) CFI_NOSEAL(bpf_ksock_release_dtor); /** - * bpf_ksock_send() - Send data through a BPF kernel socket. + * bpf_ksock_sendto() - Send data through a BPF kernel socket to a remote address. * @ks: The BPF kernel socket context. Must be an acquired reference. * @data: Pointer to the data to send. * @data__sz: Size of the data to send. + * @addr__nullable: Pointer to an IPv4 or IPv6 socket address, or NULL to use + * the connected destination. + * @addr__sz: Size of the address union, ignored when the address is NULL. * - * Sends data on a connected socket, best-effort and nonblocking. This may sleep + * Sends data to the specified address, or to the connected destination when + * the address is NULL, best-effort and nonblocking. This may sleep * (kernel_sendmsg), so it can only be called from sleepable BPF programs. * * Return: Number of bytes sent on success, negative errno on error. */ -__bpf_kfunc int bpf_ksock_send(struct bpf_ksock *ks, const void *data, - u32 data__sz) +__bpf_kfunc int bpf_ksock_sendto(struct bpf_ksock *ks, const void *data, u32 data__sz, + const union bpf_ksock_addr *addr__nullable, + u32 addr__sz) { + struct sockaddr_storage sa; struct msghdr msg = { .msg_flags = MSG_DONTWAIT, }; @@ -232,11 +244,34 @@ __bpf_kfunc int bpf_ksock_send(struct bpf_ksock *ks, const void *data, .iov_base = (void *)data, .iov_len = data__sz, }; - int ret; + int addrlen; - ret = kernel_sendmsg(ks->sock, &msg, &iov, 1, data__sz); + if (addr__nullable) { + addrlen = bpf_ksock_addr_to_sockaddr(addr__nullable, addr__sz, &sa); + if (addrlen < 0) + return addrlen; + msg.msg_name = &sa; + msg.msg_namelen = addrlen; + } - return ret; + return kernel_sendmsg(ks->sock, &msg, &iov, 1, data__sz); +} + +/** + * bpf_ksock_send() - Send data through a BPF kernel socket. + * @ks: The BPF kernel socket context. Must be an acquired reference. + * @data: Pointer to the data to send. + * @data__sz: Size of the data to send. + * + * Sends data on a connected socket, best-effort and nonblocking. This may sleep + * (kernel_sendmsg), so it can only be called from sleepable BPF programs. + * + * Return: Number of bytes sent on success, negative errno on error. + */ +__bpf_kfunc int bpf_ksock_send(struct bpf_ksock *ks, const void *data, + u32 data__sz) +{ + return bpf_ksock_sendto(ks, data, data__sz, NULL, 0); } __bpf_kfunc_end_defs(); @@ -255,6 +290,7 @@ BTF_KFUNCS_START(ksock_kfunc_btf_ids) BTF_ID_FLAGS(func, bpf_ksock_release, KF_RELEASE) BTF_ID_FLAGS(func, bpf_ksock_acquire, KF_ACQUIRE | KF_RCU | KF_RET_NULL) BTF_ID_FLAGS(func, bpf_ksock_send, KF_SLEEPABLE) +BTF_ID_FLAGS(func, bpf_ksock_sendto, KF_SLEEPABLE) BTF_KFUNCS_END(ksock_kfunc_btf_ids) #ifdef CONFIG_BPF_LSM pw-bot: cr